Messrs. Hancock & Attliey on Archichtliys sulcidens. 81 



of tlie surface-structure, which agrees with that of the other 

 bones of this fish, and that we know of no other species 

 found in our coal-shales to which they can belong. The size 

 alone would seem sufficient to determine the question. Me- 

 gulichthys is certainly a large species ; but the largest jugular 

 plate we have seen of that fish is scarcely more than 7 inches 

 long, not half the length of those in question. And, moreover, 

 its form and enamelled surface are sufficient to distinguish it, 

 though in general character it has considerable resemblance to 

 the specimens under discussion. Except those that are alto- 

 gether out of the question, the only otlier fishes of any con- 

 siderable size that occur in our coal-shales are the three large 

 species of Ctenodus : in this genus, however, the mandible is 

 too short, and the space in front between the rami too con- 

 tracted to admit of there being any large jugular plates; indeed 

 Ctenodus is understood to have no jugular plates. Un- 

 fortunately, these two enormous plates are imperfect ; but what 

 remains of each is in an excellent state of preservation, and 

 lies flattened out, the; form being completely retained : and 

 there is no difficulty in determining the entire contour; for 

 whilst one has only the posterior extremity imperfect, this 

 extremity in the other is entire. 



The right plate has the under surface exposed ; the anterior 

 portion of this is quite perfect, a small part only of the poste- 

 rior extremity, as just noticed, being wanting. In front it 

 tapers gradually to a point, and there is a notch on the inner 

 margin, about 1^ inch from the apex ; at this part the surface 

 is depressed diagonally, the depression being bounded in front 

 by a stoutish ridge. This plate, or, rather, as much of it as 

 remains, is 12 inches long and A\ inches wide. Only the 

 posterior extremity of the left plate is present ; and this frag- 

 ment is 3^ inches in length, and lies with the upper surface 

 exposed, with the inner margin in contact with the outer 

 margin of the other plate. The posterior border is obtusely 

 pointed ; but as the slope is shorter on the outer than on the 

 inner margin, the acumination is towards the outer edge. 



By the aid of these two fragments, the form of the entire 

 plate is easily determined. It is elliptical or widely fusiform, 

 with the anterior extremity pretty regularly and gradually 

 pointed, the posterior end being more abruptly and excentri- 

 cally acuminated. When perfect, these huge jugular plates 

 cannot have been less than 14 or 15 inclies in length, as, 

 judging from the specimens, it would seem evident that the 

 fragment (which is 12 inches long) of the right plate has lost 

 two or three inches of its posterior extremity. 



A fragment of a bone lies on the outer margin of the right 



