17 
MODIOLA subcarinata? 
TAB. CCX.---Fig. 1.° 
Syn. M. subcarinata? Za Marck, Foss. de Pa- 
ris, 191. Annales du Muséum @ His- 
foire Naturelle, Vol. VI. p. 122. V. 
EX. tab. 10, 7.10: 
Spec. Cuar. Oblong, smooth, gibbose ; anterior 
side keel formed, rather obtuse ; posterior lobe 
convex ; front concave. 
Tue margin of the front is arched inwards in this shell; 
whereas in M. modiolus of Linn. that edge is straight. 
The length, taking the measure obliquely, is above twice 
the width, and greater than in M. modiolus of Linn. It 
is often strongly marked by the lines of growth, and is 
very pearly beneath a thin brown epidermis. 
This is probably not the Modiola subcarinata of La 
Marck, although it agrees with the description ; but I 
must consider it as such until I obtain the means of dis- 
tinguishing them. It may probably be one of the varie- 
ties of Mytillus modiolus of Brocchi ; but as that author, 
who is apt to treat fossil species as only varieties of re- 
cent shells, does so in the present instance, it is not easy 
to determine this point. The specimens figured are the 
produce of Highgate Hill. The large one has been much 
broken by pressure, but the small one appears to retain 
its original form undisguised. 
MODIOLA bipartita. 
TAB. CCX.---Figs. 3 and 4. 
Spec. Cuar. Elongated, smooth, rather gibbose ; 
anterior side obtuse, suddenly raised above the 
posterior ; posterior lobe irregular. 
Weary related in general form to the last, but readily 
distinguished, by the separation of the posterior lobe 
