PECTEN. 69 



two species. I have never seen an intermediate form, 

 although I have examined many hundred specimens of 

 P. striatus and about fifty of P. Testae with a view to the 

 comparison. The present species has some of the sculp- 

 ture of P. tigrinus and the shape of P. striatus. The 

 colouring of P. Testae is more bright and vivid than that 

 of the other two. Some specimens are perfect gems. 

 Mediterranean examples are usually much smaller than 

 those from the North Atlantic, although I have seen 

 several of a tolerable size which were collected by S r . 

 Costa at Naples. Mr. Clark's specimen from Exmouth, 

 in my collection, was mixed with P. tigrinus ; and I am 

 rather surprised that his habit of close observation did 

 not enable him to separate them. 



It is probably the P. incomparabilis and P. vitreus 

 of Bisso; but his love of species-making seems to 

 have been so inveterate, and his collection is in such 

 a deplorable state of confusion, that it is almost hopeless 

 to attempt any identification of his names. The P. 

 vitreus of Chemnitz is quite a different species, as Phi- 

 lippi has well observed. 



7. P. stria'tus*, Muller. 



P. striatus, Mull. Zool. Dan. Prodr. p. 248, no. 2994 ; F. &H. ii. p. 281, 

 pi. Ii. f. 1-4, and (animal) pi. S. f. 2. 



Body whitish, irregularly streaked lengthwise with opaque 

 white lines : mantle edged with white and having an outer 

 fringe of extensile white cirri : ocelli 25 in number, blue- 

 black with crimson centres ; behind them is an inner fringe of 

 short white cirri : gills also furnished with 20 reddish-brown 

 ocelli, each of which surmounts the crest of a leaflet. 



Shell resembling that of P. Testae in shape; but it is rather 

 larger, thinner, and more fragile, and the sculpture (especially 

 of the upper valve) is very different. In the present species it 



* Striate. 



