170 PROCEEDINGS OF THE NATIONAL MUSEUM vol. io» 



Cardita crassidens (Broderip and Sowery, 1829) 



Plate 22, figures 7-10 



Astarte crassidens Broderip and Sowerby, 1829, p. 365. 

 Cardita borealis var. paucicostata Krause, 1885a, p. 30, pi. 3, fig. 5. 

 Venericardia crassidens Dall, 1903a, p. 949, pi. 63, fig. 9. 



Venericardia paucicostata Oldroyd, 1924, p. 112, pi. 13, fig. 3. — Kira, 1954, p. 105, 

 pi. 52, fig. 21. 



Approximately 35 specimens were collected from 18 stations ranging 

 in depth from 80 to 477 feet; the greatest number from any one station 

 was 8 from 341 feet. The largest shell measures 36.4 mm. long by 

 37.2 mm. high by 18.9 mm. in breadth, and the next largest is 35 by 

 38 by 17.8 mm. Other than the smallest specimens, the majority 

 range between 20 and 35 mm. in height. Small specimens were 

 collected as follows: 1 (3.5 by 3.2 by 1.9 mm.) from 216 feet; 3 (ranging 

 from 1.6 to 2.2 mm. in length) and 1 (3.3 by 3 by 1.8 mm.) from 184 

 feet; 1 (4.6 by 4.4 by 2.5 mm.) from 152 feet; and 4 (2.4, 3, 8, and 

 9.1 mm.) from 341 feet. 



The gonads of a specimen collected at 341 feet on Oct. 11, 1949, 

 contained eggs measuring up to 761.4/x (the average being 753/x). 

 Since there was only a thin, crystalline layer around the egg, most 

 of the egg consisted of yolk. With such a large, yolky egg, it seems 

 probable that C. crassidens is ovoviviparous. 



Other material examined: About 25 specimens from localities 

 ranging from Icy Cape and the Sea Horse Islands, Bering Strait and 

 Plover Bay to Kodiak Island. 



Discussion: Like the Point Barrow shells, these specimens vary 

 from those that are longer than high to those that are higher than 

 long, and have a periostracum ranging from a yellowish light brown 

 to an olive brown, and in others the shells are so eroded that the 

 periostracum is lacking. In some the broad ribs are clearly visible to 

 the ventral margin, in others the shell is so coarse and eroded that 

 little ribbing is discernible except in the region of the umbos. Internal 

 crenations are visible even in the most misshapen shells. 



In young specimens the length exceeds the height (pi. 22, fig. 9), 

 but in adults the height usually exceeds the length (pi. 22, fig. 7). 

 In those adults in which the length exceeds the height, the height has 

 often been foreshortened by growing in a rugged environment that 

 prevents the shell assuming a normal shape and the ventral margin 

 grows inward instead of ventrad. One specimen from 130 feet (Aug. 

 9, 1949) with a shell 23.3 by 25.6 by 15.4 mm. has the ventral and 

 antero ventral (the latter somewhat subtended) margins turned in to 

 such an extent that the breadth at the ventral margin is as great as 

 anywhere throughout the extent of the shell, making the shell boxlike 

 (see pi. 22, fig. 10). 



