CONCHIFERA. 727 
xIv. Pl. 20—22, 23, figs. 1, 2. In the mount of St Peter is found Ostrea 
larva of which the elongated crooked shell with folded margins has some 
resemblance to the larva of an insect. 
In some species the inferior shell, when the individuals are older, is 
curved upwards at the point and very thick. Of these Lamarck formed 
his genus Gryphaa. (Sp. Gryphea angulata Lam. from the coast of Peru.) 
These forms in the fossil state especially abound in the Oolite and Lias 
formations (as Gryphea arcuata Lam., Buatny. Malac. Pl. 59, fig. 4, 
Bronn Lethea, Tab. 19, figs. ta, b); hence the name Gryphite-limestone, 
in geological works. In Fxogyra Say, Sow. the point is not bent upwards, 
but sideways. Species of this form occur especially in the chalk-formations, 
Family HI. Pectinidea. Mantle open with margin thick, 
tentaculate, often ocelliferous. Foot small. Shell regular or sub- 
regular, solid, often marked by longitudinal ribs, mostly auriculate. 
Spondylus L. Shell inequivalve, adherent, mostly auriculate, 
rude or muricate. Hinge with two strong teeth in each valve and 
pit of ligament intermediate. Animal (Argus Port) with body 
compressed and margin of mantle cirrate and ocelliferous. Foot 
small, disciform, supplied with a middle cylindrical filament sus- 
taining an oval capitulum. Adductor muscle very large, central. 
Sub-genus: Plicatula Lam. Shell inauriculate, plicate ; inferior 
valve without external cardinal area. 
Sp. Spondylus plicatus L., Plicatula ramosa Lam., Canmn. Conchyl. Tab. 
47, figs. 479, 480;—Plicatula cristata Lam., Buainv. Malac. Pl. 62, fig. 2, 
GuERIN Jconogr., Moll. Pl. 25, fig. 9, &e. There are also fossil species of 
this form. 
Sub-genus : Spondylus Lam. Shell mostly auriculate. Inferior 
valve produced beyond the hinge, area in superior trigonal, flat, 
mostly divided by a median furrow. 
Sp. Spondylus Gaderopus L., Pout Test. utr. Sicil. 11. Tab. 21, figs. 20, 21, 
Tab. 22, Encycl. méth., Vers. Pl. 190, fig. 1; in the Mediterranean ;— 
Spondyl. americanus LaM., GuER. Iconogr., Moll. Pl. 25, fig. 8, &e. 
Fossil species of Spondylus are found in the chalk-formation. To Spon- 
- dylus, moreover, some fossil genera, whose characters are of no sufficient 
value, are referred by DrEsHAYES, as Podopsis Lam., Pachytes DEFR., 
Dianchora SowERBY. Comp. Ann. des Se. natur. XV. 1828, pp. 427—434, 
and the second edition of Lamarck Hist. nat. des Ani. s. vertebr. VIL. pp. 
195—108. 
Hinnites DeFr. Shell irregular, subovate or orbicular, auriculate, 
affixed. Hinge edentulous, pit of ligament narrow, deeply cut 
out. 
