140 CRETACEOUS LAMELLIBRANCHIA. 
1882. Puicaruna spinosa, J. Kiesow. Schrift der Nat. Gesellsch. in Danzig, 
n. F., vol. v, p. 241. 
1885. = inFuata, F. Nothing. Die Fauna d. baltisch. Cenoman. (Pale- 
ont. AbhandL, vol. ii), p. 15, pl. ii, fig. 3. 
1887. — — A. Peron. Hist. du Terr. de Craie (Bull. Soc. Sci. 
Hist. et Nat. de l’Yonne, ser. 3, vol. 
xii), p. 169, pl. ii, fig. 3. 
1889. — _— A. Fritsch. Stud. im Gebiete der bohm. Kreide- 
format. IV. Die Teplitz. Schicht, 
p- 86, fig. 84. 
1895. — — E. Tiessen. Zeitschr. der deutsch. geol. Gesellsch., 
vol. xlvii, p. 477. 
? 1897. — — A. Fritsch. Stud. im Gebiete der bohm. Kreide- 
format. VI. Die Chlomeker Schicht, 
p. 68, fig. 88. 
Description.—Shell oval or somewhat triangular—more distinctly oval in large 
specimens; very oblique, margins rounded. Right valve moderately convex, the 
convexity increasing considerably with age, so that in old specimens the later part 
of the valve curves considerably from the less convex earlier part. Left valve flat 
or concave. Right valve ornamented with regular, radial, slightly curved ribs, 
which are usually few in number, and bear short recumbent spines, which are 
longer at the anterior and posterior margins; a few new ribs may be introduced 
between the older ones. Left valve with similar ribs and spines. 
Measuremeits : 
qd) (2) (8) (4 () 
Length . 18 22 238 24 25 
Height’ . 22 28 21 26 28 
(2) from the Lower Chalk, Ventnor. 
(8) from the Chalk Marl, Haslingfield. 
(9) from the H. swhglobosus zone, Cherry Hinton. 
Others from the Totternhoe Stone, Burwell. 
6 
= 
(7) (8) (9) (10) (11) 
98 37 45 45 49mm. 
3088 Ae Ao” 
bo bo 
~I~1~ 
b 
6 
+} 
Affinities —From a comparison of specimens of P. radiola, @Orbigny, from the 
Aptian, with specimens of P. inflata, Sowerby, from the English Cenomanian, 
Pictet, Renevier, and Campiche came to the conclusion that the two forms could 
not be regarded as distinct species. My own observations lead me to endorse the 
opinion of those writers—that examples of the same size are inseparable. In 
the Cenomanian, however, the specimens often reach a larger size than any I 
have seen from the Lower Cretaceous; in such cases the ventral part of the valve 
is nearly smooth, or has only indistinct ribs. Figures of a large and also a small 
form from the Chalk are given by Goldfuss, and good figures of an Aptian speci- 
men by Pictet and Roux. Peron has named some very small forms from the 
Cenomanian P. Cotteawi, and considers that P. spinosa, @Orbigny, is an example 
1 Measured obliquely from the umbo to the middle of the ventral margin. 
