1862.] MOEEIS AND ROBEETS CAEBONIFEEOFS LIMESTONE. 105 



two plates are situated, which, in the memoir before alluded to, I 

 named the thoracic plates. These constitute an important item in 

 the structural economy of Ptericlitliys, inasmuch as they afford attach- 

 ment to the lateral appendages, and form the basis of support for 

 these organs in all their movements. This being undoubtedly the 

 case, as shown in specimens of every species I have examined, I am 

 at a loss to conceive how Professor Pander can have been led to assign 

 the attachment of the arms to the ventro-lateral plate, as shown in 

 the magnified figure on tab. 6 of his magnificent work on the Devonian 

 Fishes, although in the preceding plate these organs are correctly 

 drawn as appended to the thoracic plate. The thoracic plates are 

 well preserved in three of the specimens of Ptericlitliys macrocephalus, 

 and in two of them one or both arms are seen in their natural posi- 

 tion. On comparing these plates with the homologous parts of 

 other species, they differ so remarkably, that, in the absence of all 

 other characters, a specific discrepancy might be affirmed. The 

 ordinary appearance of these plates when in conjunction is that of a 

 narrow band or belt, hollowed out anteriorly in a crescentic form, 

 to allow space for the vertical movements of the head. In the 

 Farlow species these plates are quadrilateral, with an anterior margin 

 convex rather than concave, each of them being nearly half as long 

 as the anterior ventro-lateral plates (figs. 2, 3, — i i). We cannot 

 but recognize in these pecuharities characters strictly in accordance 

 Tvith the other deviations of structure from the allied species de- 

 tailed in the foregoing remarks. The greater length of the pectoral 

 organs required a stronger fulcrum, and the large-sized head a firmer 

 support. One of the specimens last forwarded for examination shows 

 the character of the surface-ornament of the plates. (See PI. III. 

 fig. 9, and woodcut, fig. 3.) This resembles the tubercular pattern 

 so constant in Ptericlitliys and Coccosteus, and off'ers no peculiarity 

 worthy of remark. The ornamentation of the arms is, however, 

 more than ordinarily coarse, and along the outer margins of these 

 organs the single row of tubercles gives, in section, the appearance 

 of a strongly serrated border. 



EXPLANATION OF PLATE III. 



llliLstrative of some new Fish Remains from Farlow and Oreton, Shropshire. 



Fig. 1 a. Palatal tooth, allied to Deltodus and Cochliodus (?). ^ g 



Fig. 1 b. The same, edge-view. B 



Fig. 2 a. Deltodus, new species. 



-p- ' 9 .' r The same, edge-views. 



Fig. 3. Deltodus, probably of the same species as fig. 2, but a larger j | ^ 



specimen (broken). | 5^ ^ "^ 



Fig. 4. Deltodus, possibly of the same species as the foregoing, but much }■ ^ "" " 

 smaller, and transversely sulcated where the surface of the 

 others is but slightly undiilated. A small, flat, quadrate 

 palatal tooth, flanged on two of its edges, accompanies this 

 specimen. 



Fig. 5. A palate, or part of a palate, composed of four subquadrate 

 and subconvex plates. 



Fig. G. Cladodus ; the only specimen of this form, ^ 







