MARINE MOLLUSCA 559 



below the periphery, and are more prominent below the anal fasciole. 

 The preceding whorls] are concave above, convex below, the ribs 

 strong and prominent on the convex portion, low and irregular on the 

 concave. Ascending the spire the concave portion widens at the ex- 

 pense of the convex, so that several earlier post-nepionic whorls are 

 concave and ribbed, with a rather acute and nodulose keel near the 

 lower suture. Below the anal fasciole the surface is strongly lyrate 

 spirally, the cords wider than the grooves and about 15 in number on 

 the last whorl. Similar spirals are faintly indicated on the anal fas- 

 ciole. Whorls 10, the earlier two rounded, smooth, forming a slightly 

 bulbous nucleus. Aperture small ; outer lip thin, retracted in a narrow 

 sinus above. Inner lip heavily calloused at its posterior termination. 

 Length 11.3 mm., diameter 3.9 mm. (Cotype in the collection of 

 the Academy of Natural Sciences, Philadelphia.) Length 12.8 mm. 

 (cotype in the collection of Stanford University, Cal.). From Tagus 

 Cove, Albemarle. 



Related to D. pallida Sowb. (Proc. Zool. Soc, 1833, p. 137), but 

 much smaller, the base less contracted, darker colored and differing in 

 various details of sculpture. Three specimens were taken, of which 

 two are in the Stanford University collection and one in the collection 

 of the Academy of Natural Sciences, Philadelphia, No. 81947. 



MOLLUSKS COLLECTED AT COCOS ISLAND. 



The following is a list of the marine shells collected at Cocos Island. 

 In the main these are Galapagos species. There are, however, a few 

 etidemic and Panama forms. The occurrence in some numbers of 

 Chlorostoma maculostriatum^ an Antillean species, is noteworthy. "~* 



Family. Species. 



PernidjE : Perna chemnitziana Orb. (?). 



ChitonidcB : Chiton siokesi Brod. 



Acm£eid« : Acmcea strigatella Cpr. 



Scarria mesoleuca Mke. 

 Fissurellidje : Fissurella virescens Sowb. 

 Neritidse : JVerita fiilg'tiratis bernkardi 'R.qcX. 



Trochidse : Chlorostoma gallinum mult tJilosu7n Stearns. 



Chlorostoma maculostriatum C. B. Ad. 

 Amaltheidae : Amalthca graya?ia Mke. 

 Planaxidse : Planaxis planicostatus Sowb. 



Cerithiidse : Ccrithium maculosum Kien. 



Muricidse : Purpura columella ris Lam. 



Purpura patula L. 



Purpura melofies Duel. 

 Columbellida; : Columbclla labrosa Sowb. 



Columbclla cribraria Lam. 

 Buccinidae : Trttonidca cinis Reeve. 



Tritonidea sanguinolcnta Duel. 

 Siphonariidae : Siphonaria gigas Sowb. 



