PERN A. 95 



Ti/jie. — From the Cambridge Greensand. In the Sedgwick Museum, Cambridge. 

 Distrilinf ion— Cambridge Greensand (derived, internal casts). 



Perna, sp. Text-figures 19, a c. 



1861. Perna lanceolata, H. G. Seeley. Auu. Mag. Nat. Hist., ser. 3, vol. vii, 



p. 122. 



Remarks. — This species (figs. 19 i;, c) was referred l)y Professor Seeley to 

 Perna lanceolata, Geiuitz,' and it presents a general resemblance to the examples 

 figured by Reuss and by d'Orbigny, but is less oblique. No satisfactory com- 

 parison, however, can be made, since the specimens from the Cambridge 

 Greensand are in the form of internal casts. 



Some examples (fig. 19 e) were named Perna lanceolata, var., by Seeley; they 

 differ from Geinitz's species in the postero-ventral part being more produced and 

 less rounded, so that the outline of the valve becomes more distinctly quadrate. By 

 this quadrilateral outline they are distinguished from P. IianUniana. 



Didrihution. — Cambridge Greensand (derived, internal casts). ^ 



Perna, sp. Text-figure 19 f. 



1861. Perna subspathulata, H. G. Seeley. Auu. Mag. Nat. Hist., ser. 3, vol. 



vii, p. 124. 



Remarks. — Internal casts wei*e regarded by Professor Seeley as examples of 

 r. snhspathnlata, Reuss,^ but they appear to dift'er from the latter in their 

 greater convexity. The height is less and the length greater than in P. ohlomja. 



Distribution. — Cambridge Greensand (derived).^ 



> ' Das Elbthalgeb. iu Sacbseu,' pt. i (1873), p. 210, pi. xlvi, fig. 8. References to other figures 

 ai-e given by Geinitz. 



* ' Die Versteiu. der bohm. Kreidofonnat.,' pt. ii (1846), p. 24, pi. xxxii, figs. 16, 17. 



3 Avicula cuneala, Seeley, may bo a Penm. Perna lissa, P. plana, and P. transverta, Seeley. 

 apjjear to be Inocerami. All four come from the Eed Limestone of Huustautou. Seeley, ' Ann. Mag. 

 Nat. Hist.,' ser. 3, vol. xiv (1864), p. 277, and vol. xvii (1866), pp. 178, 170. 



