DEEP-SEA PROTOBRANCHIA (BIVALVIA) 



121 



Fig. 30. NucuUina acuta, a & b, lateral and dorsal external views of the lectotype. ANSP 30613; c, lateral internal view of a paralectotype from the same 

 lot. Scales = lmm. 



Conrad, may include those figured by him. Comparison with the 

 figures (Conrad, 1831 and 1845) shows that it is impossible to say 

 which, if any one, was figured nor is it possible to be absolutely 

 certain that these are the specimens from which the original descrip- 

 tion was made, although we believe that they are. Thus, the intact 

 shell from lot 30613 has been chosen as the lectotype, the remainder 

 being paralectotypes. 



Campbell (1993) listed Leda jamaicensis d'Orbigny 1846. Leda 



Fig. 31. Nuculana acuta. Lateral and dorsal external views of a shell, 

 from Atlantis 283 station 2 from the North America Basin. Scales = 

 lmm. 



inomuta A.Adams 1 856 and L.unca Gould 1 862 as synonyms of N. 

 acuta. Verrill (1882) describes in detail differences that he found 

 between N. acuta and Ljamaicensis and L.unca which cast doubt as 

 to the synonymy, although Dall ( 1886) maintains the synonymy of 

 L. jamaicensis. Similarly, we have doubts as to synonymy with 

 Linornata A.Adams which is a 'gibbose'. 'fuscous', 'sulcate' spe- 

 cies from New Guinea, Thus, although Nuculana acuta is a 

 well-described species (e.g. Verrill 1882, 1884; Dall, 1886; Abbott, 

 1974) because there are closely related species in the Atlantic and 

 elsewhere, we include a description here. It occurs off the East coast 

 of North America, in the Caribbean Sea and off Brazil at depths from 

 the outer shelf to lower slope depths, 97-2909m (James, 1972). 



Shell description (Figs 30, 31) 



Shell moderately large, elongate, somewhat inflated, rostrate, 

 ornamented with deep concentric ridges flattened at the apex, rostral 

 ridge from umbo to ventral limit of rostrum, very faint radial ridge 

 from umbo to antero-ventral margin, yellow periostracum; lunule 



Fig. 32. Nuculana acuta. Internal morphology as seen from the right side 

 of a specimen from Atlantis II station 197 from the North America Basin. 

 For identification of the parts see text- figure 7, p. 106. Scale = lmm. 



