NO. 9 MARINE INVERTEBRATES, ALASKA — MacGINITIE 1 73 



Musculns disc or s var. laevigatus Gray and M. corrugatus (Gray) 

 were common in hauls from 130 to 741 feet. Specimens of laevigatus 

 under 20 mm. in length were found nestled in the interstices between 

 barnacles and in old holdfasts of tunicates. Specimens exceeding 20 

 mm. in length were nearly always covered with a byssal net, although 

 no eggs were found within the net. On the other hand, a specimen of 

 corrugatus 12.7 mm. in length that was taken from 184 feet was sur- 

 rounded by a byssal net that enclosed a large number of embryonic 

 clams still within the tgg membrane but with definite valves developed. 

 Eight of the embryonic clams averaged 428.5 microns in length. Mus- 

 culus niger (Gray) was less abundant than the above species. Only 

 two specimens over 30 mm. in length were taken (one of these at 741 

 feet, the other washed ashore). The other specimens did not exceed 

 15 mm. in length. 



About 16 specimens of Astarte horealis Schumann were dredged 

 at depths of 80 to 438 feet, and others were taken from Eluitkak Pass. 

 Old shells from Eluitkak Pass were filled with silt and so tightly 

 closed that they were difficult to open. Since living shells as well as 

 old ones are often badly eroded at the umbos, it was often impossible 

 to distinguish between live and dead specimens without opening the 

 shells. A. montagui Dillwyn compares favorably in abundance with 

 Hiatella arctica and Macoma calcarea. It was dredged from 80 to 

 453 feet, being especially abundant at 216 and 453 feet. There is 

 great variation in proportions and color in this species, with the re- 

 sult that it has been described many times. Even living shells are 

 often encrusted with colonies of bryozoans or with small barnacles. 

 A specimen 18 mm. long appears to be between 2 and 3 years old, 

 and a specimen 25 mm. long is about 5 years old. This species, prob- 

 ably because of its accessibility, forms a favorite food of Natica and 

 Polinices. 



One to three specimens of Cardita crassidens (Broderip) were 

 taken in nearly every haul from 80 to 453 feet. A Cardita 24 mm. 

 long and 22 mm. high was 4 years old, and another 24 mm. long and 

 20 mm. high was 5 years old. 



Four specimens of Clinocardium ciliatum (Fabricius), from 45 to 

 62 mm. in length were taken from no, 152, 453, and 522 feet. 



About 30 living Serripes groenlandicus (Bruguiere) were dredged 

 from depths of 80 to 420 feet, with no more than three in any one 

 haul. The shell of this species is very brittle and often cracks when it 

 becomes dry. In Serripes from Point Barrow the lines indicating a 

 cessation of growth while the animal is producing eggs or sperm are 

 about as marked as the annual lines of growth, making the determina- 



