CARBONIFEROUS FOSSILS. 
40r) 
acce.ssory anterior pedal scars. The A uthmromija differ from Carboni- 
colu by i)Ossessing a broadly e.xpanded and truncate posterior region 
and a well-defined gonial ridge. 
The X((l)idifes iwe ineiinivalve Mytiloid forms, characterized by the 
anteriorly directed and subterminal umbones, and externally resem- 
bling l)reis.‘<eiisia in shape and ornamentation as well as in the 
distinct presence of the byssal notch. 
The fossils of this formation are - 
I’XIOXID.K. 
Carhu))ir(il(i riciifd (.1. Sow.), 
— V. vhnml)oidaUs Hind, 
rnifjiildfn ( Ityi'kliolt), 
toitirjiKi Hinil, 
aqiiiliiKi (J. deC. Sow.), 
cuHcifonnis Hind, 
dcgans (Kirkby), 
gibbuxfi Hind, 
iniriilaris Hind, 
obtiisd Hind, 
ora/ix (Martin), 
jiol ntoiifrnxix { l?ro w n ), 
robiix/ii (J. de ('. Sow.), 
}-iii/iixii (Hrown), 
xiini/ix (Hrown), 
xiibcijiixtricfd (J. Sow.), 
xubrofini(bi ( Hrown), 
tiirgii/d (Hrown). 
I'inti { KirkLy), 
A)if/irdrt)iii>/d dddjiixi Salter, 
— V. c.r/idiixd Hind. 
cdlciferd Hind, 
(hiinbrdtd (.1. de ('. Sow.), 
Idun'oldtd Hind, 
td vix V. xcoficd Ktlieridge jr., 
Anthraroini/a ininimn (Ludwig), 
— V. cdrinatd Hind, i 
mndioldfix (,I. de C. Sow.), 
— V. cKvtdtn (Hrown), 
oboratn Hind, 
phillipsi (Williamson), 
pnlchra Hind, 
pumild Salter, 
scncx Salter, 
xubccnfndix Sal ter, 
xiibpdrdllcld ( Portloek), 
ivdcncinixix Hind, 
uvirdi Etheridge, 
willidiiixniii (Hrown), 
— V. dbtdxd (Ludwig). 
MVTILID.i;. 
Xaidditcx Cdrinata (J. de C. Sow.), 
— V. tiiiiiidd Itind, 
cvdxxd (Fleming), 
— \'. iiiodioli/uniiix (Hrown), 
cloiigdtd Hind, 
nuKjua Hind, 
'inodiol((]'ix (J. de C. Sow.), 
obcxn (Fitheridge jr. ), 
quudrata (J. de C. Sow.), 
tridnguldrix (J. de ('. Sow.). 
'I’be i\lEStizoic {peao'i, middle ; ^w//, life) or Secondary strata include 
the Trias, the Jurassic and the Cretaceous formations, and are charac- 
terized by the predominating development of the Pelecypoda and also 
contain fossil remains of genera long extinct in this country, but still 
fiourisbing in lands more distant from the evolutionary centre. 
'I'be Mehoiiddu', which now characterize the iMalayan peninsula, 
the African t.^)ntinent, and are tilso numerous in Eastern North 
America tuid other primitive regions, were formerly abundant in this 
country, as testified by their remains in the Oolite, the Cretaceous 
and succeeding strata. Corblcnla and rnlo were also numerous in 
the secondary rocks, l)ut the former is no longer found in this country, 
but restricted to distant areas, and the latter have noiv but three 
representatives, although in Eastern North America they abound at 
the present day. Neritina, Vivipura, and Valvata, are all archaic 
