98 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DeC. 5, 



The remains of Fteraspides before referred to are, I believe, 

 undescribed. There are two species, differing essentially in form, 

 although nearly allied in structure. Both possess under the outer 

 dermal covering the granular texture, on the existence of which 

 M. Agassiz * laid so much stress in pronouncing his opinion on the 

 head of Cephalaspis Lloydii; but instead of granules, resting on 

 laminae, the lower end of each of the granules fits into an irregular 

 hexagon (PI. II. fig. 2 c). In addition, the bony enamel of the Old 

 Red fish is wholly wanting. Both had a dermal covering, marked 

 with very distinct longitudinal striae f, which in most of the speci- 

 mens has wholly or partially disappeared. 



Many of the specimens from the Tilestone are in a state of disinte- 

 gration ; the granules lie separated on the surface, and the hexagons, 

 thus exposed, are visible to the naked eye. To use Mr. Miller's 

 description in reference to Cheiracanthus and Biplacanthus, — " The 

 cranium seems to have been covered, as in the Shark family, by 

 skin, and the skin by minute shagreen-like scales ; and all of the 

 interior cerebral framework which appears underneath exists simply 

 as faint impressions of an undivided body, covered by what seems 

 to be osseous points, — bony molecules, it is probable, which were 

 encrusted in the cartilage J." 



The most prominent features of the species illustrated by PI. II. 

 fig. 2. are a round snout, followed by a sharp projection on either side, 

 with horns attached to the sides of the posterior part of the head. 

 The strise of the horns are almost regularly parallel and so continue, 

 though with less regularity, over the sharp projections and round 

 the snout. On the upper, or raised portion of the head, the striae 

 proceed from the ridge in somewhat curved longitudinal lines, every 

 fourth one of which is larger and more prominent than the others, 

 until they meet in the centre above the snout. On the underside of 

 the sharp projections before referred to are protuberances which 

 seem to be projecting horny eyes, similar to those of crustaceans. 



The other species (PI. II. fig. 1) has an almost square, slightly in- 

 curved snout, without lateral horns, or trace of eyes ; the striae are 

 less regular, and there is an indication of an upper jaw. For other 

 details I must refer to the drawings and the specimens, which 

 accompany this notice. 



These fossils occur in places in considerable abundance. Like 

 the PterygotuSy with which they are often found in juxtaposition, 

 they appear to have congregated in masses and to have frequented 

 the same haunts. 



Of another specimen, which occupies a doubtful place between 

 the Crustaceans and Fish, I must defer an account until I can fur- 

 nish an accurate illustration of it. The portion I have found is 



* See * The Silurian System,' p. 595. 



t Such longitudinal striae are visible on the head of Cephalaspis Hoydii in the 

 Museum at Ludlow. 

 X Footprints of the Creator, p. 43. 



