from Achanarras Quarry ^ Caithness. 



481 



Bemarhs on the foregoing Species. 



1. Dipte7-us Valenciennesii. — Tliis is bj far the most com- 

 mon fish at Aclianarrns, and, so far as the external characters 

 of the species are concerned, the specimens are the most 

 beautiful which I have seen from any locality in Scotland. 

 They occur from 6 to 15 inches in length. 



2. Ifesacanthics, sp. — Specimens of a small Mesacanthus 

 are not uncommon, but liardly in a sufKciently good state of 

 preservation for accurate identification as to species. In size 

 and the commonly twisted or contorted condition of the body 

 they resemble M. pusillus^ Ag., of the AIoray-Firth beds. 



The genus Mesacanthus was instituted by myself in 1888* 

 for tliose small species previously referred to Acanihodes [A. 

 pmsiHuSj Ag., A. Mitchelli, Eg., A. Peachii, Eg.) which, 



Fij?. 1. 



Outline of Acanihodes sulcatus, Ag., much reduced. 

 ■), pectoral spines ; v, ventral spines ; a, anal ; c?, dorsal. 



Fiff. 2. 





Outline of Mesacayithus MitchelU, Eg., natural size. 

 sp., intermediate spines ; the other letters as in fig. 1. 



though resembling that genus in having one dorsal spine 

 placed posteriorly to the anal, have in addition a pair of 

 minute intermediate spines on the belly between the pectoral 

 and ventral ones. Messrs. Smith Woodward and Sherboru 

 have, however, in their recently-published ' Catalogue of 



* Geol, Mag. dec. iii. vol, v. p. 611. 



