18 CRETACEOUS LAMELLIBRANCHIA. 
author are apparently all casts, so that an exact comparison cannot be made. 
Geinitz considers that specimens which he obtained from the Plinerkalk of 
Strehlen and Weinbéhla, and from the Plinermergel of Walkmiihle near Pirna, 
belong to N. pectinata ; but they appear to differ from the English specimens in 
that the posterior part of the shell is rounded and relatively longer. 
The variations seen in different examples of this species are chiefly in the 
proportions of length and breadth, and in the form of the curve of the ventral 
margin, the latter giving to the shell a triangular or a rhomboidal outline. 
N. striatula, Rémer,' N. truncata, Nilsson,’ and N. Blochmanni, Geinitz,> have 
been regarded by Geinitz and Reuss as identical with N. pectinata, Sowerby. 
Types.—The types, now in the British Museum, are labelled “ Sussex.’ The 
Specimens figured by Mantell (except fig. 5) and those figured by Gardner are 
likewise preserved in the British Museum. 
Distribution.—Through all the zones of the Gault at Folkestone; Gault of 
Burham, Aylesford, Black Ven, Devizes, Campton (Hast Bedfordshire), Ely and 
Haddenham (Cambs.); Marls with Bel. minimus at Speeton; Upper Greensand 
of Warminster (cast only seen). 
Nocuza pxotinata, Sowerby, var. crnrm, Gardner, 1884. Plate III, figs. 14a, b, 15. 
1884. Nucuna pecrrnata, var. creTa, J. S. Gardner. Quart. Journ. Geol. Soe., 
vol. xl, p. 182. 
Remarks.—This form appears to differ from N. pectinata, Sowerby, only in 
being proportionately shorter. The surface of the shell, in the two specimens 
which I have seen, is somewhat abraded, but I do not think that the ornamentation 
differs from that of N. pectinata. 
Without more examples I am unable to say whether this form is really distinct 
from N, pectinata. 
Measurements : 
Length . : : . ; 3 15 mm. 
Height . , ; k 5 ; ‘ 1 oe 
Thickness. ON. 
Types.—In the Museum of Practical Geology (Nos. 6449, 6450). 
Distribution.—Blackdown Greensand.! 
* “Die Verstein. der norddeutsch. Kreidegeb.’ (1841), p. 68, pl. viii, fig. 26 (the type comes 
from the Plinerkalk of Strehlen). 
? «Petrif. Suecana’ (1827), p. 16, pl. v, fig. 6. 
3 *Char. der Schicht. u. Petref. d. sachs. Kreidegeb.,’ pt. 1i (1840), p. 50, pl. x, fig. 8. 
+ Erroneously stated by Gardner to come from the Grey Chalk of Devon. 
