Proceedings of the United States National Museum

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U.S. Government Printing Office, 1899 - Acrotus willoughbyi - 14 pages
 

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Page 297 - ... latter are subordinate to the spiral sculpture and are more conspicuous on the lower part of the body whorl. Color dull-cream white, with (in the example before me) two obscure, broad, pale rufous bands on the body whorl. Spire short, obtusely conical. Whorls six (probably apex in example somewhat eroded) ; suture distinct, narrowly channeled. Aperture about two-thirds the length of the shell (not quite 9 mm.), acutely angular above, rounded and effuse below, finely lirate and glossy within,...
Page 827 - Di'-pth. — 30 feet, sandy bottom. Body oval, somewhat flattened. Surface smooth; color light yellow with markings of brown. Head with the anterior margin much broader than the posterior margin, produced in front but not wholly concealing the basal joints of the first pair of antenna;, and somewhat raised, forming two small conve-x elevations. The antero-lateral margin is likewise produced, forming an acute angular projection, which extends in a lateral direction beyond the post-lateral margin of...
Page 849 - ... flagellum obsolete. The second pair of antenna* are also extremely short, equal in length to the width of the head, with rudimentary flagellum, composed of about five joints, and with peduncular joints dilated. Mandibles have the cutting part composed of five teeth; palp, three-jointed. The thoracic segments are subequal in length, with lateral edges produced, but not laciniate, and separated from each other by latera
Page 849 - Mus., XXI, 1899, pp. 859-860; Ann. Mag. Nat. Hist. (7), IV, 1899, pp. 326-327; American Naturalist XXXIV, 1900, p. 300. Locality. — Monterey Bay, California. Surface of body smooth. Color very peculiar and striking. The head is brown. The first thoracic segment is perfectly white, without any markings. The second, third, and fourth segments are brown. The fifth and sixth are white. The seventh thoracic segment and the caudal segment are brown. This peculiar marking gives the body a striped appearance....
Page 827 - The epimera are almost twice as broad as long; those of the fifth segment extend downward, with the anterior margin straight, making the length and breadth about equal, and forming almost square epimera; in the...
Page 826 - ... the first segment. Thoracic segments subequal. Epimera broad and extending downward, forming an angle with the segments. First abdominal segment with two low tubercles close together, situated one on either side of the median line; terminal segment triangular, with apex narrowly rounded and sides slightly infolded, forming a small opening when seen from below. Six low tubercles are situated on this segment, two in longitudinal series on either side of the median line — the lower ones being...
Page 824 - The epiniera are square with rounded posterior angles. The penultimate abdominal segment is crossed by suture lines, indicative of coalesced segments. The terminal segment is triangular, terminating posteriorly in two teeth separated by a narrow, rounded, funnel-shaped sinus. This segment is very convex, and bears two longitudinal ridges on either side of the median line. The uropoda do not exceed in length the extremity of the terminal segment. Both branches are rounded posteriorly and are similar...
Page 841 - The tirst is composed of the first three pairs of feet, which are comparatively stout and increase in length to the third segment. The second series begins on the fourth segment with a pair of short feet, which fold transversely, the other pairs are successively longer and fold backward. The feet of the second series are much more slender than those of the first. The dactyli of all are bi-unguiculate.
Page 819 - Uropoda and terminal segment not ciliated. Eyes small. c. Posterior angles of first segment of body prominent or produced, very often acute; posterior angles of the following segments increasing gradually in length, the first of these very often scarcely produced, the posterior ones very often produced, abruptly longer than the first.
Page 826 - ... side of the median line, and with two spots on the first abdominal segment, one on either side of the median line. Head small. First pair of antennae reach almost to the posterior margin of the first thoracic segment. Second pair extend fully to the posterior margin of the first segment. Thoracic segments subequal. Epimera broad and extending downward, forming an angle with the segments. First abdominal segment with two low tubercles close together, situated one on either side of the median line;...

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