DESCRIPTION OF THE FOSSIL REMAINS. 55 



three inches in length, and about an inch and a half in breadth ; the wings, 

 in every specimen yet discovered, are depressed and inclined to the sides ; 

 and in no instance has any portion of the caudal organ been detected, in the 

 least remaining tracery or impression. The carapace, in all the plates and 

 lateral appendages, is fully defined ; and, as remarked b}' Hugh Miller upon a 

 reconsideration of my specimens presented to the Edinburgh Geological and 

 Agricultural Museum, '* one of the most striking specific distinctions of the 

 Pamphractus Andersoni consists in the length and bulk of the arms, and the 

 comparatively great prominence of those angular projections by which they 

 are studded on the edges," — projections which seem to be but expansions of 

 those confluent lines of tubercles by wbich the arms of all the numerous 

 species of the genus pterichthys are fringed. 



GlypU/potnus minor. — Agassiz. Pl. II. 



" I am only acquainted," says M. Agassiz, " with a single specimen of this 

 genus, from the collection of Professor Jameson, which I at first took for a 

 Platygnathus. Afterwards, when I had leisure to make a more minute exa- 

 mination, I was soon convinced that, notwithstanding the resemblance of its 

 exterior with the platygnathus, it was distinguished by particulars of struc- 

 ture too important to admit of its remaining associated with this type, and 

 consequently I was obliged to form a separate genus." 



We may now perhaps express our surprise that, by so discriminating a 

 judge of fossil fishes, a moment's hesitation could have existed as to the wide 

 and obvious distinctions manifest in every outline of the specimens in question. 

 That the Glyptopomus and the Asterolepis might for a time be confounded, 

 one can readily admit, more especially so long as only the scales and plates 

 of the latter were the sole means of comparison. But in nothing do the 

 platygnathus and the glyptopomus, in general appearance and external struc- 

 ture, seem to bear the slightest resemblance. 



The differences, as pointed out in the Monographie du Vieux Gres Rouge, 

 upon subsequent examination are very clearly stated. " The scales of the 

 platygnathus are round and imbricated, so that the posterior edge of one scale 

 covers the anterior edge of the following one, and possessing in this respect 

 all the characteristics of the scales of the caelacanths ; on the other hand, 

 those of the glyptopomus resemble the scales of the sauroids, which are 

 rhomboidal or quadrangular, placed in juxtaposition to each other, and are 

 never imbricated. Moreover, the platygnathi are elongated fishes, furnished 

 with a long tail and a very powerful rudder fin ; whereas the glyptopomi are 

 much thicker, and their tails shorter and less branching in the bundles of 

 rays. The ornaments on the scales of the glyptopomus are deeply marked, 

 resembling those of the caelacanths, while all the plates of the head are 

 strongly tuberculated with a beautiful shagreen enamel." 



This description was given by M. Agassiz upon inspection of the specimen 

 now in the British Museum, which has a large thick flat body, approaching 

 in form to the Holoptychius Andersoni. The head is proportionally small, 



