OF SOUTHERN INDIA. 425 



ears uneqixal, the anterior being the larger, in the right valve provided with a deep 

 byssal sinus ; hinge-line straight, ligament marginal, linear, cartilage lodged in a 

 usually central and triangular pit, from the top of which often one to thi-ee ribs 

 radiate ; muscular scar large, sub-central. Type, P. varitis, Linne. 



The name Fecten should be reserved for the species strictly represented by 

 the above type. The shells are generally somewhat higher than long, the surface 

 is covered with numerous scabrous, denticulated or scaly, radiating ribs and striae, 

 and the anterior ear of the right valve is generally somewhat ascending, the ears 

 themselves being of moderate size in proportion to that of the shell itself. The 

 typical Pect'mes occur through all formations from the oldest upwards, and are most 

 numerous at the present time. 



3 a. Chlamys, Bolten, 1798. P. hifrons. Lam., should be considered as the 

 type of this sub-genus. It represents a group of Tectines which are generally 

 somewhat inequivalve, of a broadly rounded form, ornamented with largish, trans- 

 versally finely serrated or striated radiating ribs, and with comparatively large, sub- 

 equal ears. Among other typical forms of this sub-genus, I would quote P. opercu- 

 laris, Lam., leopardus, Reeve, Solaris and micleus, Born, squamatiis, Gmel., &c. ; 

 but I would exclude islandtcus, which is stated to belong to this sub-ffenus, though 

 it does not appear to differ from Fectoi as restricted. H. and A. Adams also quote 

 ornatus, Linne, which is a Fecten, and vUreus and strictttis, which may better be 

 classed with Fseudamusium. 



3 6. lAropecten, Con., 1867, (Lyropecten* Am. Journ. Conch., Ill, p. 6). 

 Somewhat inequivalve, with moderately developed unequal ears, valves ornamented 

 with strong nodulose and striated ribs, near the umbones always somewhat irre- 

 gularly gibbose ; hiuge with a few oblique teeth on each side of the ligamental 

 fosse. Type, P. nodosus, Linn. 



There are a few tertiary species from N. America referred to this sub-genus, 

 and it is very likely also that species like the cretaceous P. septemplicatus, Nilss., 

 and a few others, belong to it. 



3 c. Fallium, Martini, 1773, fDentipecten, Riipp.). Shell generally some- 

 what higher than long, equilateral, sub-equivalve, with moderately numerous, 

 strong radiating ribs, small, sub-equal ears, more or less distinctly toothed on the 

 internal hinge-margin. Type, P. p)lica, Linn. 



3 d. Cmnptonectes, Agassiz, 1864, (teste Meek in Check-list, cret. and jur. 

 inverteb. foss., N. America, p. 28, (No. 891) ; Smith. Misc. Coll., No. 177 ; = Ehur- 

 neopecten, Con., 1867, Am. Journ. Conch., Ill, p. 140). Valves sub-equal, moder- 

 ately flattened, ovate or sub-ovate, with well developed, or rather small, unequal 

 ears, the anterior of the right valve with a byssal sinus, surface marked with 

 fine radiating, curved, striae, sej)arated by punctated grooves. Type, P. lens, 



* Conrad, loc. cit., discusses the affinities of his Lyropecten to Pallium, Klein, which, he says, is founded on 

 Pect. pallium. Klein has no genus of that name, for what he calls Pallium variegatum, &o., &c., is a form of his 

 second species in the " genus Pecten" (vide Ostrac., pp. 130 — 131), and therefore the name Pallium could not have been 

 considered as generic by Klein. 



5 M 



