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SUPPLEMENT TO THE CRAG MOLLUSCA. 



Pholas parva, Pennant. Supplement, Tab. X, fig. 26. 



Pholas parva, Penn. Brit. Zool., vol. iv, p. 77, pi. xl, fig. 13 ? 



— dactyloides, Desk. 2nd ed., Lam., vol. vi, p. 45. 



— ligamentina, Id. Elem. Conch., pi. hi, figs. 11, 12. 



— tuberculata, Turton. Brit. Biv., p. 5, pi. i, figs. 7, 8. 



Length, f inch. 



Locality, lied Crag, Waldringfield. 



Mr. Alfred Bell and Mr. Charlesworth lately obtained some blocks of clayey material 

 from the nodule pits at Waldringfield, in which were lodged several specimens of this 

 species, with the valves united in their natural position, and I am indebted to both those 

 gentlemen for specimens. 



The Crag fossil corresponds with the short variety of the existing species, which is 

 nearly equilateral, but the imbricated radiations are closer and more numerous than upon 

 any recent specimen that I have seen. 



Pholas brevis, S. Wood. Supplement, Tab. X, fig. 24 a, b. 

 Locality. Cor. Crag, Sutton. 



In the ' Crag Moll.,' vol. ii, p. 296, I spoke of a fragment of Pholas crispata having 

 been found by myself in the Cor. Crag. This fragment I now believe does not belong- 

 to that species, and I have had it represented as above (Tab. X, fig. 24 a). I have also 

 met with several other large fragments and some small perfect specimens (one of which I 

 have figured 24 b) which appear to me to be the young of the same species, although in 

 these young specimens the imbricated radiations approach much nearer to the dorsal 

 margin on the siphonal side than they do on the large fragment. In the latter, however, 

 they are faintly visible over this part, and may have become obsolete during the growth 

 of the shell. The small specimens show a highly reflected dorsal edge behind the 

 umbonal region, but this part is broken off in the larger specimens. In our present 

 species the imbricated rays cover, even in the adult shell, as shown by the large fragment, 

 more or less of the posterior half of the shell, which is not the case with crispata. In 

 other respects the large fragment resembles crispata. The proportions also of both the 

 figured specimens differ from those of Ph. crispata. 



As the other fragments and imperfect small specimens, of which I have many, 

 uniformly maintain the characters above referred to, the species seems to differ from 

 any other known to me, and I have accordingly proposed for it the above name. 



