408 
PROCEEDINGS OF THE ACADEMY OF 
Localities.— Marshall and the grindstone quarries at Pt. aux Barques, be¬ 
longing to the Marshall group. 
The dorsal valve greatly resembles that of R. circularis. 
Rhynchonella Marshallensis, n. sp.—Shell of medium size ; dorsal valve 
very ventricose, with the middle region somewhat flattened, and all the mar¬ 
gins abruptly deflected—the anterior at nearly right angles ; beak prominent, 
obtuse, incurved ; cardinal slopes short, making with each other an angle of 
about 100 c . Surface of valve marked by about 27 medium-sized rounded, 
radiating plications, two or three of which are implanted on each lateral ex¬ 
tremity, some of the plications reaching the beak. A shallow mesial fold 
rises in about the middle of the valve aud embraces seven plications. The 
mesial septum extends about one-eighth the length of the valve. 
Length of the dorsal valve *58 (100) ; breadth *62 (107 ; convoxity, -30 (52). 
Locality. —Marshall. 
Rhynchonella camerifera, n. sp.—Shell of moderate size, tumid; beak of 
ventral valve projecting and slightly upturned; cardinal slopes straight, at 
right angles ; sides of the shell rounded ; front margin similarily rounded or 
somewhat straight, not unfrequently produced on one side of the mesial sinus. 
Dorsal valve nearly circular, a little more convex than the ventral, most con¬ 
vex anterior to the middle, and rather abruptly bent down in front. Ventral 
valve with a shallow sinus, which extends back about one-fourth the length 
of the valve, corresponding to the fold in the dorsal valve ; most convex be¬ 
tween the beak and the middle ; dental plates parallel, well developed ; teeth 
at right angles, elongate, growing stouter anteriorly, with handsomely crenu- 
lated margins ; mesial partition of the dorsal valve, extending nearly one half 
its length, thickening near the beak, to give space for the excavation of a 
small chamber within the septum. Shell with 20 or 21 (a variety ? with 16) 
sharp plications, of which three or four are comprised in the mesial sinus ; 
these are crossed by a few squamulose concentric wrinkles ; shell structure 
fibrous. 
Length of an average specimen *38 (100); breadth *34 (90); thickness, 
•19 (50). 
Locality. —Pt. aux Barques, in a conglomeritic ferruginous sandstone over- 
lying the gritstones of the Marshall group—myriads of casts sometimes form¬ 
ing, with Centronella Julia , the whole mass of the rock. 
The small chamber in the mesial septum of the dorsal valve is an interest¬ 
ing and unique character. On a similar cameration of the septnm of the ven¬ 
tral valve of some Cyrtise the genus Cyrtina has been founded ; and Professor 
King established his Camarophoria pn the formation of an arch in the ventral 
valve by the approximation of the dental plates. 
This species has the external appearance of the young of R. incuebescens , 
but, amongst thousands, none attain proportions very different from those 
given above, 
Rhynchonella barquensis, n. sp.—Shell small, transversely oval, thin. 
Ventral valve with a moderately prominent beak and slightly curved cardinal 
slopes ; greatest tumidity near the beak, from which the surface descends in 
a nearly right plane to the anterior margin, and with little convexity to the 
right and left margins. Dorsal valve flattish, most inflated in the middle. 
Mesial fold and sinus small, traceable one fifth or sixth the length of the shell, 
embracing two or three sharp plications, of which the entire surface of each 
valve receives about 12 or 13. Dental plates of ventral valve parallel; me¬ 
sial septum of dorsal valve camerated as in R. camerifera. 
Length *30 (100); breadth -32 (107) ; thickness *13 (43). 
Locality. —Grindstone quarries, Pt. aux Barques, with R. camerifera . 
Rhynchonella subcircularis, n. sp.—Shell small, cuneate-rotund, subtumid. 
[Sept. 
