128 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 18, 



Coccosteus miceospondtltjs. — In the generic characters of this 

 genus, Prof. M'Coy describes the bodies of the vertebrae as rarely 

 ossified. The reservation is made in favour of this species, in which 

 he states the bodies of the vertebrae to be separately ossified. If 

 this were really the case, a structural deviation of such importance 

 could scarcely be limited to a mere specific character. A laborious 

 examination of all the specimens I have had access to, and of this 

 one in particular, has satisfied me that in this genus the bodies of 

 the vertebrae were never ossified, but that the chorda dorsalis was 

 persistent in its embryonic condition. The form of the neur- 

 apophyses is very singular. The lower extremity of each of these 

 swells out into a thick clavate process, simulating a vertebral body 

 slightly abraded, in consequence of which the mistake has been 

 made, by more observers than one, of considering them vertebral 

 centra. Under this impression Prof. M'Coy named this species C. 

 microspondylus. The bodies which he considers ossified vertebral 

 centra are in fact the lower ends of the neurapophyses ; and the 

 " dermal bones of the dorsal fin reversed" are the hasmapophyses, 

 the broad interval between the sets of spines being the position of 

 the chorda dorsalis. I cannot discover that this species differs in 

 any respect from Coccosteus decipiens. The latter species was ori- 

 ginally named Coccosteus latus by Agassiz ; but as he cancelled this 

 specific title, and replaced it by decipiens in the description of the 

 species, Prof. M'Coy would do well to adopt the latter, instead of 

 reviving the obsolete name. 



Coccosteus pusillus. — In one of the numbers of the ' Witness ' 

 newspaper, of December 1848, Hugh Miller described a " mi- 

 niature Coccosteus," of which he found great numbers in a quarry 

 near Kirkwall, to which he gave the name Coccosteus minor*. Prof. 

 M'Coy published his description of Coccosteus pusillus, in the ' Annals 

 of Natural History ' for November 1848. Should the species be 

 the same, of whieh there is little doubt, the latter name has the 

 priority. 



Coccosteus trigonaspis. — This species is founded upon the an- 

 terior median subthoracic plate of Coccosteus decipiens, and must 

 consequently be cancelled. 



This paper has already so far exceded the limits I originally con- 

 templated, that I must postpone the further consideration of the 

 subject to a future period. 



SUPPLEMENT. 



I have put together in the form of a supplement several extracts 

 from letters received from the late Hugh Miller, at the time when 

 we were both occupied with the investigation of the details of Coc- 

 costeus. I am not aware that these observations have been made 



* See Supplement ; and ' Cruise of the Betsey,' p. 394. 



