NO. 9 MARINE INVERTEBRATES, ALASKA — MacGINITIE 1 75 



Qass GASTROPODA 



The Point Barrow gastropods present a great deal of data on prob- 

 lems of Arctic distribution, reproduction, and feeding. Variation 

 within a species is often great. The majority of the species lay egg 

 capsules containing large-yolked eggs or nurse eggs or some form 

 of nutriment that permits the development of large nonpelagic larvae 

 or larvae with a short pelagic life ; a few retain their eggs until the 

 larvae are in the crawling stage. Because of the rapid filling of the 

 ocean bottom by erosion from shore, empty shells dredged at Point 

 Barrow are never very old. 



Order PTEROPODA 



Although Spiratella hclicina (Phipps) was reported to be abundant 

 during the summer of 1947, only two specimens were collected dur- 

 ing August 1948, and none was seen in 1949 and 1950. 



Clione limacina Phipps was exceedingly abundant at times during 

 the summer of 1948 — on August 12, for example — and was common 

 in 1949 and 1950. Larval forms were present in the plankton through- 

 out the winter of 1949. Both larval and adult forms were plentiful 

 alongshore on July 20, 1950. This species forms an important food 

 for whales. 



Order OPISTHOBRANCHIATA 



A single specimen of Retusa nitidula (Loven) was taken at 477 feet. 

 One Cylkhna occulta Mighels was taken through the ice on January 

 25, 1950, and another near shore on July 13 of that year. Two speci- 

 mens of Diaphana minuta Brown were collected, one at 741 feet, the 

 other at 295 feet. 



What is believed to be Aldisa zetlandica (Alder and Hancock) was 

 taken in the gravel zone in from 10 to 15 feet of water, one on July 

 20 and two on September 8, 1948. Three others washed ashore on 

 October 16, 1949. This species seems to prefer the occasional patches 

 of sand that have been segregated from the gravel. It ingests detritus 

 containing considerable sand. 



Eighteen specimens of what is believed to be Dendronotus frondosus 

 (Ascanius) were washed ashore and three were dredged (140 and 

 150 feet). A translucent white species of Dendronotus, with the tips 

 of the cerata chalk white, was infrequently washed ashore and two 

 were dredged at 150 feet. 



Four specimens of what may be Coryphella salmonacea (Cou- 

 thouy) washed ashore on September 6 and October 16, 1949. 



