224 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 2 



Holotype: No. 708 (Calif. Acad. Sci. Paleo. Type Coll.), from 

 Loc. 27,229 (C.A.S.), from 3 to 9 fms. in Bahia Honda, Panama. L. 

 G. Hertlein collector. Approximately 600 additional specimens were 

 dredged in the same locality. 



The edge of the aperture does not look fully mature, but in the 

 large number of specimens there is nothing to indicate a later stage of 

 growth. The only west coast species approximating this in size and 

 number of rings is Caecum parvuni C. B. Adams, ^^ also from Panama, 

 but it is said to have "acute-edged moderately prominent distant rings." 

 The specimens so identified in this collection are quite distinct from the 

 present species. Caecum dalli Bartsch,^^ from California, has much the 

 same appearance but is a larger shell wifh broader, flat topped rings. 



This species is named for Bahia Honda [Deep Bay], Panama, 

 where a collection was made of many species of the smaller mollusks as 

 well as a number of species belonging to the larger forms. 



Caecum richthofeni Strong & Hertlein, new species 



Plate 20, Fig. 11 



Shell consisting of a moderately curved, opaque, white tube of 

 nearly uniform diameter; sculptured with 27 raised rings which are 

 flatly reflected toward the aperture or anterior end of the tube, the edges 

 nearly in contact on the concave side of the tube but separated by open 

 spaces of varying width on the convex side; the flat top of the rings 

 marked with close, microscopic, longitudinal threads; the last 3 rings 

 separated from the balance by a deep, rounded sulcus, showing faint 

 annular striations in the bottom; the last ring contracted to form a 

 broad, sloping face surrounding the aperture; aperture circular, at a 

 slight angle to the curved axis of the tube, the last ring being much 

 narrower on the concave than on the convex side of the tube; posterior 

 end of the tube somewhat contracted, closed by a deep-seated plug en- 

 circled by a high rim ; a clawlike spur rises from the center of the plug 

 with the point extending beyond the rim on the convex side of the tube. 

 Operculum concave, horn colored, with a central nucleus and about 

 12 concentric rings. The type measures: length, 2.9 mm; diameter of 

 tube, 0.8 mm. 



PP 



48 Caecum parvum C. B. Adams, Ann. Lyceum Nat. Hist. New York, 1852, 

 pp. 387, (No. 217), 535. "Panama." 



■iS Caecum dalli Bartsch, Jour. Washington Acad. Sci., vol. 10, no. 20, 

 December 4, 1920, p. 568. Type locality, "San Diego," California. Also known 

 at many stations from San Diego to Lower California. 



