SMITH : ON THE GENUS SCUTUS. 263 



Had hot the type, which I have seen, in the Linnean Cabinet, 

 been preserved the species would have had to be abandoned as 

 unrecognisable. However, the shell marked with the number 

 (767) of the 'Systema' definitely decides which species Linnaeus 

 really had before him. This is figured by Hanley in his 'Ipsa 

 Linnsei Conchylia,' pi. iii., f. 4. The conclusion arrived at by 

 Chemnitz ('Der Naturforscher,' 1787, stiick 22, p. 23) that this 

 species belonged to the gen-us Pinna, rests upon Linne's reference 

 to Petiver's figure, which being that of a Lingula has somewhat 

 the form of a Pinna. It is about an inch in length, narrows just 

 a little anteriorly and the sculpture consists of imbricating con- 

 centric lamellse of growth with undulating edges^ and scarcely 

 displays any of the corrugation which in some specimens extends 

 over the entire surface as in the typical granulatus. This was 

 described by Blainville from a young shell, for he says that it is 

 smaller than his breviculus, the type of which in the Museum 

 measures exactly one inch. It does not however follow that the 

 fullgrown gramdatus would be entirely "granulous," for many 

 specimens are corrugated at the apex on a surface which we may 

 presume equals the size of Blainville's type, yet on the rest of the 

 shell show scarcely any or no traces of this corrugation particularly 

 towards the margin. 



The variety corrugatus as figured by Reeve is peculiar for its 

 subparallel lateral margins, a feature not at all constant, for in the 

 museum series of specimens the closest gradation from this form 

 to that which narrows considerably anteriorly is observable. 



P. imbricatus Quoy and Gaim., judging from the figure in 

 the 'Astrolabe,' is a trifle narrower than the Linnean type and the 

 posterior end when viewed laterally appears to be up-curved 

 somewhat, a character as equally gradational in a series of 

 specimens as the form of the outline, the width in proportion to 

 the length, and the position of the apex. 



