578 



W. J. Crozier, 



60 



50 



30 



Material. 



During the summer of 1912 a number of specimens of Dosinia 

 discus (Reeve, 1850) were secured at Beaufort, N. C.^) The genus 

 Dosinia is considered to be one of the most highly developed of the 

 Veneridae; its shell is distinguished from that of other members of 

 the family by a number of characteristics, which include the long, 

 ^jj angular, ascending palliai 



sinus and the moderate con- 

 vexity of its almost circular 

 valves (Plate 35 Fig. 1). The 

 valves are covered by a thin 

 lustrous periostracum and are 

 marked externally by a series 

 of regular annuli, which in- 

 crease in width toward the 

 edge of the shell. The range 

 of the species is given by 

 Dall (1902) as extending 

 along the coast line from 

 Cape May, Virginia, to Vera 

 Cruz, Mexico. At Beaufort 

 it lives in sandy flats about a foot below the surface, occurring 

 practically up to low water mark. My specimens were obtained 

 from sand thrown up from a depth of about 12 feet by a 

 dredge engaged in clearing a harbor channel; apparently, therefore, 

 the depth range of Dosinia is greater than Osborn (1887) and 

 Aller (1912) have indicated. Living animals only were taken for 

 measurement, since in these there was no shell erosion; no other 

 selection was exercised. As shown in Fig. A, the length as an 

 indication of size, ranged, from 1,5 to 7,5 centimeters, those shells 

 being most abundant that were about 5 cm long. One hundred and 

 eightj'^-five shells were measured. 



S-S 65 75 cms. 



Fig. A. 

 Length-frequency distribution. 



1) This material was collected while I was in the temporary employ 

 of the U. 8. Bureau of Fisheries. 1 am indebted to the Bureau for the 

 priviligcs of the Beaufort laboratory. 



