THE MOUNT DESERT REGION 239 



C. TUBERCULATA (G. 0. Sars). (G. 0. Sars, 1925, p. 192, pi. 

 88. ) Taken twice on muddy bottoms, in 40 to 70 feet of water. 

 Stations: D46; P lOB. 



C. PRocTERi Blake. (Blake, 1929, p. 13, fig. 6.) Taken twice 

 with the preceding. 



C. LEioDERMA (Norman) comb. nov. (Brady and Norman, 

 1889, p. 139, pi. 15, figs. 12, 13.) In spite of the remarkable 

 form of the shell, the hinge and the appendages show this to 

 be a normal species of Cythereis. It occurred twice in mud, 

 in 10 to 40 feet of water. The species is new to New England. 

 Stations: D 59 ; P lOB. 



C. (Hemicythere) concinna (Jones) comb. nov. (Jones, 

 1856, p. 29, pi. 4, fig. 7; G. 0. Sars, 1925, p. 189, pi. 87, fig. 1.) 

 Our specimens agree excellently with the figure given by 

 Jones, but show slight deviations from Sars' figures of the 

 shell. It occurs on mud, in 20 to 72 feet of water. Stations : 

 D 32, 46, 48, 54, 115 ; P lOB. 



C. Hemicythere) arenicola Cushman comb. nov. (Cush- 

 man, 1906, p. 379, pi. 36, figs. 97-107.) Rather common on 

 sand, in about 6 feet of water, at S 21. 



Subgenus PTERYGOCYTHEREIS Blake nov. 



This subgenus is distinguished by the shape of the shell 

 and by the pellucid, hyaline nature of its substance. The 

 shell seen from above is rather broadly triangular, due to two 

 prominent ventrolateral wings. The outer margin of these 

 wings is almost straight, considering the tips of the spinous 

 processes, of which the wings are fundamentally composed, 

 as marking the margin. Other similar conical processes may 

 occur elsewhere on the shell, particularly alongside the hinge 

 and at the two ends of the shell. 



The species for which the appendages are known have the 

 fifth to seventh limbs very notably attenuated. 



Cythereis jonesi Baird is designated as the type of the 

 subgenus which contains, in addition, C. mucronata G. 0. 

 Sars, inexpecfafa Blake, and cormda (Roemer). 



