Cope.] t> [April 17, 



The specimen was obtained near Agua Coraprida, near Bahia, by Mr. 

 Joseph Mawson. I dedicate the species to him with much pleasure, in 

 recognition of the valuable service rendered by his collection in the pres- 

 ent investigation. 



PVCNODUS FLABELIiATUS, Sp. nOV. 



A slab of limestone contains a skeleton of this fish, but the latter is in 

 several points imperfect. The head anterior to the orbit is wanting, and 

 the superior half of the anterior dorsal region is broken away. The ven- 

 tral fins are lost. Some isolated teeth are of the proper size to belong to 

 this species, and will be mentioned later. 



The outline of the profile of the body is discoidal, and the axis of the 

 skull (vomer, etc.) is directed obliquely downwards at an obtuse angle 

 with the vertebral column. This requires an extensive production of tbe 

 operculum above and posterior to its articulation with the hyomandibular. 

 The clavicle is slender, while the coracoid is produced backwards be- 

 low the pectoral fin, its superior border being concave to the first rib, 

 which is overlapped by the posterior edge. The coracoid also extends 

 downwards and forwards as usual. The four basilar bones of the pectoral 

 fin are rod-like, and are moderately expanded distally. The determina- 

 tion of this point is of much importance in fixing the position of the Pyc- 

 nodontidce in the system. The basis of the dorsal and ventral fins de- 

 scend steeply downwards to a narrow and very short caudal peduncle. 

 The caudal fin is of characteristic form. Its lobes are long, but they di- 

 verge so widely that the posterior edge of the fin is slightly convex from 

 tip to tip. Radii, D. 53 ; C. 3 + 40 + 2 ; A. 24. 



The constitution of the vertebral column is not easy to make out. Only 

 the anterior half is preserved. This displays the usual superior and inferior 

 plates. In the present species the edges of these are in contact, so that 

 the condition of the centrum, if there be any, as to ossification, is not posi- 

 tively determinable. The neural spines above their basal expansions 

 are connected by a series of longitudinal teeth which interlock closely so 

 as to resemble a series of ribs. On examination it is found that half of 

 these originate from one neural arch, and half from the other, there being 

 six or seven in all. A slight protuberance, probably for the rib-head, ap- 

 pears 3 mm. below them. The true ribs are broadly alate, so as to form a 

 continuous wall. The rhabdopleurs agree in number with the vertebra;, 

 and are present to the end of the vertical fins. On the caudal region they 

 extend downwards .66 the length of the haemal spines. The latter ex- 

 tend to the superior apices of the interhamials. The rhabdopleurs are 

 not segmented as is represented in some species of this family. The 

 caudal fin includes one or two vertebrae. There are two short, widely ex- 

 panded hypurals, much as in Physoclystous fishes where they are distinct. 



Vertebra;, D. 19 ; C. 15 or 16. 



Measurements. M. 



Total length to anterior edge of orbit 172 



Longitudinal diameter of orbit 016 



