82 Journal of the Asiatic Society of Bengal. [N.8., XIX, 
plus oe encore’.!. Nyst’s description makes it quite clear 
that the species is not a true Pecten. Sowerby also pointe 
out the affinity of this species with P. scion oetes the type 
of the genus Amussium, but the absence of the internal ribs 
shows that it cannct be referred to that genus, while the 
published description shows that it is more ‘allied to Pseuda- 
mussium than to any other genus as already mentioned by 
Stoliczka.2 The Hathab specimens are entirely different. 
Fedden apparently depended upon d’Archiac and Haime for 
this identification, but these authors, evidently, were not 
sanguine regarding the identity of the Hala Range specimen 
with Pecten corneus chiefly on account of the fact that the valve 
is ‘‘composé de deux couches principales distinctes, lune 
externe....l'autre interne ou sous-jacente, et presentant in 
systéme de stries rayonnantes nombreuses (80 a 90), droites. 
d’égale profondeur, mais inégalement espacées ’.° A cursory 
examination of the Hathab specimens shows that these 
characters do not appertain to them. 
he valves are very thin, rounded and slightly inequi- 
lateral. The beak is acute with a straight hinge-line. The 
ears are nearly equal and those of the right valve form a 
small synclinal arch where they join the beak, while the ears 
of the left valve form a perfect ‘straight border at the umbonal 
portion. The byssal notch is fairly prominent. The external 
surface is practically smooth excepting some very indistinct con- 
centric lines of growth. In the interior of the valves there are 
usually 30 to 34 ribs all arranged in pairs. This number is 
fairly constant in shells of different sizes showing that in the 
younger specimens the ribs are much pressed together 
This species has some relationship with 4. cristatus Broun 
but a little consideration shows that Bronn’s species is more 
swollen, has the external concentric markings more prominent 
and has, below the resilial pit, curved ridges the like of which 
is not found in the specimens from Hathab.* This species 
may also be compared with Pecten (Pleuronectia) placunoides 
Martin described from Java, but Martin’s species has a larger 
number cf internal ribs.’ The number of ribs found with 
P. corneus (?) d’Arch and Haime is still greater, while its 
external surface is pee concentrically striated. It has 
got a very close similarity with the cage Pecten (Amussium) 
uronectes Linn,’ but in the latt ‘the number o 
internal ribs is smaller and the mesitial. pit is a little shallower. 
— are, however, many characters in which these two 
I oo d. = we Polyp. pie de Belg.. p. 299. 
s Vo 
3 Desc a : : Tr e p. 269. 
+ Goldfuss, a Germ.. p. 77, Tav. 99, figs. ~~ 
itr. Z. Geol. Ost-Asiens und Austral., Vol. 1, Tab. fig. °2. 
6 Fora ran Sibliognaehs of this and sie species of Amuss? um. 
= 
5 
poe ae 
