THE CRETACEOUS FORMATION. 
13 
A somewhat allied species, having two projections or bosses on each valve, instead 
of one only, occurs in the Forest-marble. 
No. 4. Cythere Faba, Betiss. Tab. II, fig. 4 a — c. 
Ci'THERiNA Faba, Reuss. Verstein. Bolim. Kreidf. p. 104, n. 9, pi. xxiv, fig. 13. 
INCH. 
Length, Jg- Detritus, Charing. 
Height, 
Thickness, .^’ 3 - Chalk-marl, Bohemia (Reuss). 
Carapace irregular oblong, somewhat bean-shaped ; anterior half narrower than the 
posterior. Dorsal border elliptical ; ventral incurved at its anterior third ; anterior 
extremity obliquely rounded ; posterior subacute. 
Dorsal aspect compressed oval ; anterior oval. 
This species (of which we have but one specimen) appears to be identical with 
C. Faba, Reuss, described by him as found in the Pliinermergel of Bohemia. In the 
Upper Oolite there is a Cythere, occurring in great numbers, which in its young state 
is like the species under notice, but when adult, is somewhat elongated and incurved 
on the dorsal and ventral margins, not unlike var. pyriformis of C. amyydaloides, 
Cornuel (Ent. foss. &c., pi. 8, fig. 11). 
No. 5. Cythere Bairdiana, 7iobis. Tab. II, fig. 5 a — c. 
INCH. 
Length, .^’ 3 - Greensand, Farringdon. 
Height, 3 C 
Thickness, 
Carapace-valve (right) somewhat triangular, convex, obliquely rounded anteriorly ; 
subacute yjosAn’or/y' ; punctated; punctations coarse, arranged somewhat longitudinally; 
Dorsal margin somewhat produced at the anterior hinge ; ventral margin slightly in- 
curved. Anterior hinge provided with a prominent, oblong tooth, with a cavity on the 
inside at its base. The valve in profile nearly straight, rather less gibbous at the 
anterior than at the posterior extremity. A single valve, with its characters some- 
what obscured by crystallization, was the only specimen found ; it closely approaches 
C. Munster, (Jahrbuch 1838, p. 516, n. 6, pi. vi, fig. 6,) but is very much 
smaller, more obtuse posteriorly, and differs materially in the character of its anterior 
hinge, having a prominent hinge-tooth, which is obsolete in C. Miilleri, and a large oval 
tooth-socket, which in C. Miilleri is long and narrow. 
This species we have named in compliment to Dr. Baird, who has so greatly 
enriched the sciences of Zoology and Comparative Anatomy by his researches in the 
natural history of Entomostraca, &c. 
