84 BULLETIN 68, UNITED STATES NATIONAL MUSEUM. 



TURBONILLA (PYRGISCUS) MORCHI Dall and Bartsch. 



Plate 7, figs. 6, 6a. 



TurhoniUa {Pyrgiscus) rnorcki Dall and Bartsch, Prof. U. S. Nat. Miis., vol. 33, 

 1907, pp. 505, 506, pi. 45, figs. ], la. 



Shell broadly elongate-conic, the j)osterior third of the exposed 

 portion of the whorls on the s])ire and a narrow area about the 

 umbilical region flesh-colored, the rest of the shell light chestnut 

 brown. Nuclear whorls two and one-half, small, smooth, forming a 

 depressed helicoid spire which has its axis at right angles to the axis 

 of the succeeding turns and is about one-fifth immersed in the first of 

 them. Exposed portion of the post-nuclear whorls flattened in the 

 middle, posterior fourth sloping gently toward the summit, which is 

 closely appressed to the preceding turn; the anterior portion slopes 

 more abruptly, roundly toward the periphery. The whorls are orna- 

 mented by strong rather distantly spaced, moderately acute, slightly 

 protractive axial ribs, of which 18 occur upon the first three, 16 on the 

 next three, 18 on the seventh, and 20 upon the penultimate turn. 

 The ribs weaken slightly and become somewhat flattened as they 

 approach the constricted sutures. Intercostal spaces broad, almost 

 double the width of the ribs, crossed by 7, equal and equally spaced, 

 deeply incised spiral lines, which extend up on the sides of the ribs and 

 feebly across them. The space between the second and third lines 

 appears slightly nodulose on the ribs. Periphery of the last turn 

 angulated, crossed by the continuations of the ribs, which disappear 

 as they pass on to the short and well-rounded base. Base marked by 

 13 continuous incised spiral lines of about equal strength which are 

 much more closely spaced near the umbilicus than the periphery, the 

 distance between the succeeding striations diminishing in regular 

 ratio from the periphery to the umbilical area, the first two below the 

 periphery being considerably more distantly spaced than the rest, the 

 spaces inclosed between them being about equal to the space inclosed 

 between the spiral lines on the spire. Aperture subquadrate, posterior 

 angle acute, outer lip thin, showing the external sculpture within; 

 columella slender, oblique, somewhat twisted and slightly revolute. 



The type (Cat. no. 173081, U.S.N.M.) has nine post-nuclear whorls 

 and measures: Length 6.4 mm., diameter 2 mm. It was collected 

 by Mr. H. N. Lowe at Long Beach, California. Another specimen is 

 in the collection of the University of California from station 122, near 

 Redondo. Another (Cat. no. 176622, U.S.N.M.) was dredged by 

 Mr. John Paine in 8 fathoms off Catalina Island. Five (Cat. no. 

 196230, U.S.N.M.) were collected by Mr. H. N. Lowe at San Diego, 

 and four additional specimens from the same locality are in Mr. 

 Lowe's collection. One, collected at station 83, off San Diego, is in 

 the collection of the University of California. 



This species is nearest related to Turhonilla (Pyrgiscus) latifundia 

 Dall and Bartsch, from the post-Pliocene of San Pedro, California. 



