AVICULOPECTEN. 127 



Remarks. — Avicula Damnoniensis, Sow., as obtained from Marwood, varies so 

 very much in shape, that it was divided by Phillips into three varieties ; it appears 

 probable, however, that this is in a large degree due to the squeezing of the beds 

 and the decayed state of the specimens, in which the ornament is more or less 

 destroyed. Still it is probable that the species did really vary considerably. 



The shells from the Pilton beds were separated as A. cancellata by Phillips, but 

 there seems no good reason for this. They are perhaps smaller, more compact in 

 shape, and very regularly ornamented, but these points are probably due to 

 individual accident or to preservation. Sowerby's type seems to agree with a fine 

 specimen from West Angle Bay, which shows from different parts of its surface 

 that, though the hind wing may in some states of preservation seem without 

 radiations, it really possessed them ; but the absence of radiations on the wing is 

 the only character which Phillips mentions as definitely distinguishing Sowerby's 

 species from his own ; while another character (the contour of the hind wing) 

 which Phillips mentioned in A. cancellata is equally seen in many Marwood 

 specimens of A. Damnoniensis. Probably if the latter specimens were in good 

 preservation the supposed differences would disappear. 



It appears probable that Pt. Salamanca, Hall, is also identical. In the defective 

 state of our specimens it is difficult to be sure of exact details of shape, but any dis- 

 crepancies that may be observable are such as might easily be accounted for by 

 incidental causes. Moreover the differences between Pt. Salamanca, Hall, and 

 Pt. Sao, Hall, seem so slight that they can hardly be more than varietal in 

 a group of shells which we know from other species to be subject to much 

 individual variation. 



Affinities. — From the South Devon species of Actinopteria , as well as from Actino- 

 pteria intermedia, GBhlert, 1 sp., it is distinguished by the shape of its wing and the 

 fineness of its ornament. 



5. Genus — Aviculopecten, M'Coy, 1852. 

 1. Aviculopecten transversus, Sowerby, sp. Plate XVI, figs. 1 — 4. 



1S40. Pecten transversus, Sowerby. Geol. Trans., ser. 2, vol. v, pt. 3, pi. liii, 



fig. 3. 

 1841. — — Phillips. Pal. Poss., p. 46, pi. xxi. fig. 77. 



1844. — — M'Coy. Syn. Carb. Poss. Ireland, p. 101. 



1855. Aviculopecten transversa, M'Coy. Brit. Pal. Poss., p. 393. 

 1893. — — Collins. Trans. Eoy. Geol. Soc. Cornwall. 



vol. xi, p. 36. 



1 1881, CEhlert, 'Mem. Soc. Geol. Pr.,' ser. 3, vol. ii, p. 21, pi. iii, figs. 1— 1 c. 



