DELPHINULA. oF 
Descr. Sub-orbicular, equivalve, inequilateral, ventricose, cor- 
roded at the umbones, thick, covered with a thick epidermis; 
hinge with three cardinal and two remote lateral teeth in each 
valve. Muscular impressions two in each valve; palleal impres- 
sion not sinuated. Obs. This genus is distinguished from Venus, 
Cytherea and Cyprina by having two remote lateral teeth; 
and from Cyclas by the thickness of theshell. Fig. 113, C. 
fuscata. 
CYRENOIDES. Joannis. Cyrenetia, Deshayes. Fam. Con- 
ques Fluviatiles, Lam. Descr. Equivalve, sub-equilateral, ventri- 
cose, thin, covered witha reddish brown epidermis, corroded at 
the umbones; with a slight posterior fold. Hinge thin, with 
three diverging cardinal teeth in each valve, and a very slight 
posterior fold in the right valve. Ligament not very tumid. 
Obs. This fresh-water shell differs from Cyclas and Cyrena in 
the want of lateral teeth, and from the latter in the thinness of 
the shell. Fig. 114. 
CYRTIA. Dalman. (Kupros, curtos, gibbose.) Fam. Brachiopoda, 
Lam. Descr. “Hinge rectilinear; with the back elevated 
into a semicone or half-pyramid, the cardinal side perpendicu- 
larly plane.”? - Obs. This genus of fossil Brachiopoda forms 
part of the genus Spirifer, Sow. C. exporrecta, (Anomites, 
exporrecta, Nonnul,) fig. 204. 
CYTHERA’A. Lam. Fam. Conques Marines. Lam. Descr. 
Equivalve, inequilateral, oval, lenticular or sub-trigonal; hinge 
with two or more short diverging cardinal teeth, and one anterior 
approximate lateral tooth in each valve. Obs. The Cytherez 
are distinguished from the Veneres by the lateral tooth. C. 
Meretrix, fig. 117, and 117, a. b. c. d. 
DECA’CERA. Bl. The second family of the order Cryptodi- 
branchiata, containing the genera Calmar and Sepia, which 
have no shells. 
DECATOPEC’TEN. Riippell. Prceren Plica, Linn. Fig. 172. 
DECIDUOUS. (De-cado, falldown.) A shell is described as 
deciduous when there is a tendency in the apex of the spire to 
fall off, as in Bulimus decollatus, fig. 289. 
DECOL'LATED. (Decollari, to be beheaded,) The apex or 
nucleus of some shells is composed of a transparent, glassy 
substance, much more fragile than the rest; and this part 
being deserted by the animal, which lives in the lower whorls, it 
is exposed to accident and the decomposing power of water. 
When this part of the shell consequently falls off, it is said to be 
decollated. Hw. Bulinus decollatus, fig. 289. 
DELPHIN'ULA. Lam. (Delphinus,adolphin.) Fam. Scala- 
riens, Lam. Cricostomata, Bl. Descr. Turbinated, orbicular, 
depressed, thick, rugose; whorls few, angulated, branched at the 
angles; aperture pearly, rounded or sub-quadrate; peritreme 
