OF SOUTHERN INDIA. 
29 
On tlie inner surface of the test the interamhul acral plates are very much 
swollen, thick, somewhat irregularly shaped, separated hy deep grooves ; the 
amhulacral areas are depressed. Fig. od on plate V shows the great number of 
small plates which surround the mouth. 
Localities . — Near Yermanoor, in a soft yellowish white sandstone with various 
Cilioj)oda ; at Comarapolliam and south-east of Kaudoor, in a greyish sandstone ; 
very common at the two first named, loss so at the last, place. 
Forma Hon . — Arrialoor grouj). 
VIII. Germs. — CASSIDULUS, Lamar'ck, 1801. 
This genus includes a groat numher of species, mostly of moderate or small 
size, ovate or somewhat angularly ovate, moderately convex above, flat below, with 
the oral region usually slightly de 2 )rcsscd ; apex and mouth somewhat eccentric, the 
former composed of four genital and five, often mdistinct, ocular plates ; the latter 
is pentagonal, surrounded hy five strongly marked lobes, between which the phyl- 
lodia are well marked, composed of only two series of pores ; anus at the top of a 
more or less oblique terminal vertical depression ; ambulacra small, suhpetaloid, not 
extending to the iieriphery of the test ; pores simple, not yoked or connected hy 
grooves in each series ; upper surface finely granular, lower with larger tubercles 
and a flattened, finely granular longitudinal hand through the centre. 
The Cassiduli occur in cretaceous and tertiary deposits. They are represented 
in South India by four species, two of which had been described as Nucleolites 
hy Forbes, who considered Fij(jordujnclms as a suhgenus of it. D’Orbigny, follow- 
ing Agassiz, redescrihed these two species under Fygorhynchus, and Desor, in his 
Synopsis (p. 299), quotes them under the same genus, although at p. 297 he dis- 
tinctly maintains that the species of that genus only occur in tertiary deposits. 
There scarcely appears to be any difference between Fijgordiynehus and Cassidulus, 
except that the former has the petals extending to near the periphery and 
tlie pores in each series connected by grooves, or yoked, while the petals in 
Cassidulus are shorter, sometimes almost lanceolate, and the pores ai’e not con- 
nected hy grooves. The lower surface is slightly depressed round the mouth in 
both genera. 
Having regard to those distinguishing characters, the Indian species appear to 
me to be referable to Cassidulus and not to FyyorJtynclius, to which they were refciTed 
hy previous authors. As a peculiarity of several of the South Indian Cassiduli, I 
have to notice that the left anterior genital plate is sometimes very small or almost 
obsolete, without a special pore, or with only a slight indication of it, hut I do not 
think that the character is sufficiently important to necessitate a generic separa- 
tion of these species from Cassidulus. Agassiz described in 18G9 a new genus 
under the name of Neolampas with only three genital plates, hut the thin struc- 
ture of the test and position of the anus, &c., conspicuously differ from other 
( fi9 ) 
