THE PERMIAN FISHES OF NORTH AMERICA 15Q 



pressed denticles throughout the upper two-thirds of the entire length; 

 surface smooth or very finely striated longitudinally." 



Genus DIACRANODUS Garman. (Plates 28, 29, and part of 30.) 

 Bull. Mus. Compar. Zool., xii, 1885, p. 30. 



The genus Diacranodus is at present known from crania and teeth 

 only; it is therefore impossible to compare it in all details of its anatomy 

 with Pleuracanthus. The crania of the two, however, seem to be sufficiently 

 different to justify their separation generically. The characters of the 

 cranium of Diacranodus are well brought out in the figures in plates 28 

 and 29, which are based on the types and one of the referred specimens of the 

 type species, D. texensis. A restoration is also given, plate 29, figures i, i«. 



Revised description of genus (based on skull) : 



1. Cranium fiddle-shaped; more shark-like than ray-like, as shown 



by the smallish rostral fontanelle. 



2. Nasal capsules, auditory capsules, and postorbital processes well 



developed. 



3. A pair of elongated bars (trabeculse?), on the under side, in 



the median axis of the cranium, inclosing between them a 

 small fossa (pituitary.''). 



4. Foramen magnum, on the under side of cranium, in the basi- 



sphenoid region. 



5. Posterior face of cranium cup-shaped (for the articulation of 



the spine?). 



6. Teeth as in Pleuracanthus. 



Diacranodus texensis (Cope). (Plates 28, 29, and 30, figs. 9-9*.) 



1883. Didymodus (?) compressus (Newb.) Cope, Proc, Acad. Nat. Sci. Phila., p. 108. 



1884. Didymodus compressus (Newb.), Cope, Proc. Amer. Philos. Soc, xxi, p. 585, i pi. 



1884. Didymodus compressus (Newb.), Cope, Amer. Nat., xviii, pp. 413 and 818, pi. 



zziii. 



1885. Pleuracanthus compressus (Newb.), Cope, Proc. Amer. Philos. Soc, xxii, p. 406. 

 1885. Diacranodus compressus (Newb.), Garman, Bull. Mus. Compar. Zool., xii, p. 30. 

 1890. Didymodus texensis Cope, Trans. Amer. Philos. Soc, n. s., xvi, p. 285. 



1900. Pleuracanthus compressus (Newb.), Case, Journ. Geol., viii, p. 701. 



Cotypes: 



1. A complete, badly crushed cranium, figured by Cope in ventral 



view (erroneously interpreted as dorsal), 1884, loc. cit., plate, 

 fig. I. No. 7928 Am. Mus. 



2. The anterior portion of a cranium, figured by Cope, loc. cit., plate, 



fig. 4. This memoir, pi. 28, figs, i, la. No. 7929 Am. Mus. 



3. The posterior half of a cranium, figured by Cope, loc. cit., plate, 



figs. 2, 3 (ventral view, erroneously labeled as dorsal). This 

 memoir, pi. 28, figs. 2, 2a. No. 7930 Am. Mus. 



4. The facial portion of a cranium, showing upper and lower jaws 



from right side, and the hyomandlbular, naturally articulated. 

 Also two isolated teeth which probably do not belong with 

 this head. Cope, loc. cit., plate, figs. 5 and 6. This memoir, 

 pi. 29, fig. 2. No. 7117 Am, Mus. 

 All from the Red Beds, Northwest Texas. 



