64 CONCHOLOGY. 
P. angulatus. P. striatularis. 
P, palleus. P. pectinatus. 
P, zonalis. P. rubeus. 
P. glycimeris. P. pectiniformis. 
P. undulatus. P. nummarius. 
P. scriptus. P. radiatus. 
P. stellatus. Pp, vitreus. 
P. violacescens. P. inscriptus. 
P. aggregatus. P. cinerosus. 
4, Genus Mucula. Pl. VIII. 
Animal. Body subtriquetral ; mantle open in its inferior half 
only, with whole edges, denticulated throughout the extent of the 
back, without posterior prolongation; foot very large, thin at the 
root, enlarged into a wide oval disk, the edges of which are fur- 
nished with tentacular digitations; anterior buccal appendages, 
pretty long, pointed, stiff, and applied one against the other like 
jaws ; the posterior ones also stiff and vertical. 
Shell. More or less thick, subtriquetral, equivalved, inequila- 
teral, with summits contiguous and inclined anteriorly ; hinge 
similar, formed by a numerous series of very sharp teeth, pecti- 
nated and arranged in a line interrupted under the summit; liga- 
ment internal, short, inserted in a little oblique pit in each valve ; 
two muscular impressions. Inhabits the British and American 
seas. Forty-five living species. Four fossil. 
Nucula lanceolata. Nucula rostrata. 
N. pella. N. Nicobarica. ° 
N. obliqua. N. Margaritacea. 
N. elongata. N. Costellata. 
N. tellinoides. N. gibbosa. 
N 
N 
N 
N 
N. crenifera. . eburnea. 
N. Arctica. . polita. 
N. curvirostra. . nasuta. 
N. glacialis. . fabula. 
N. fluviatilis. N. Elenensis. 
N. minuta. N. cuneata. 
NN. para. N. striata. 
N. Mauritiania. N. rugulosa. 
