284 SPONDYLIDA. 
hinge-line very long, edentulous. Avic. prisca, Munst. (cxxxii, 
89), from permian rocks. 
Bryopuina, Carpenter, 1864. 
Distr.—B. setosa, Carp. On alge, at Cape St. Lucas, L. 
California. 
Shell like a minute Pinna, with pointed beaks; upper margin 
straight, with a strong internal ligament, anteriorly at the byssal 
sinus somewhat insinuated, ventrally and posteriorly rounded 
and gaping ; posterior muscular sear subcentral, indistinct. 
The animal is stated to be viviparous; and in form “like a 
minute Pinna, ora byansviense Margaritophora without ears, or 
a Perna without pits.” Its length is only 0°13 inch and the 
width 0-2 inch, but it is said to be adult. The structure of the 
shell agrees with that of Pinna, being fibrous externally, nacreous 
internally. 
SusorpeR MONOMYARTA. 
Shell with a single subcentral or subposterior muscular 
impression. 
( Pectinacea. ) 
Famity SPONDYLID A. 
Shell inequivalve, right valve largest, attached at the beak ; 
cartilage internal, in a median pit; hinge-teeth two in each valve, 
sometimes without teeth; outer surface with radiating ribs, 
often spiniferous. 
PriicaTuLa, Lamarck, 1801. 
Etym.—Plicatus, plaited. 
Distr.—9 sp. W. Indies, India, Philippines, Australia, West 
America. Fossil, 106 sp. Trias —; United States, Europe, 
Algeria, India. P. Mantelli, Lea, Alabama, has the valves eared. 
P. ramosa, Linn. (cxxxi, 69). 
Shell irregular, attached by the umbo of the right valve; valves 
smooth or plaited ; hinge-area obscure ; cartilage quite internal ; 
hinge teeth two in each valve; adductor scar simple. 
Animal resembles Spondylus. 
HARPAX (Parkinson, 1811), Deslongchamps, 1858. Hinge of 
attached valve consisting of a flattened triangular plate, 
traversed by a central more or less perpendicular ligamental 
furrow, exterior to which are slightly marked diverging sulei to 
receive the elevated borders of the ligamental groove in the 
other valve; the outer borders of the plate form lengthened and 
elevated dental processes. Hinge-plate of free valve traversed 
mesially by the ligamental groove, the borders to which are 
elevated and but slightly diverging; exterior to these are 
