220 a 



More complete specimens of species of this genus show that vertebrae 

 of the type which I have described (p. 240) under the name of Anogmius 

 belong to them.* The latter name may be used for this genus should it be 

 ascertained that our species cannot be included in the one typified by the 

 European Packyrhizodus basalis, Dixon. 



The posterior half or more of the cranium of a species allied to the 

 P. latimentum is preserved, with both the maxillary bone and teeth, and the 

 basioccipital element separated from its connections, adherent. Above, the 

 latter exhibits two sub triangular articular faces in close contact, for the exoc- 

 cipitals. Below, there is a strong median carina, or crest, which is strongly 

 grooved on the free margin; this groove probably represents the muscular 

 tube. The exoccipital facets stand on a horizontal triangular face ; but, in 

 front of this, the sides of the bone are beveled to the plane of the base, for 

 sutural adaptation to the prootic, etc. 



The structure of the superior walls of the skull may be largely discerned 

 in this specimen. The cranium is flat and wide, and pressure has probably 

 somewhat increased the effect in this instance. Exoccipital, supraoccipital, 

 epiotic, pterolic, parietal, and frontal bones are clearly distinguishable; but 

 there are points at which the sutures are obscure. The best defined are the 

 epiotics, which are subtriangular bones, presenting the apex inward, and 

 bearing a small round facet for the supratemporal on the posterior angle. 

 The pterotics and postfrontals may be easily distinguished from adjoining 

 bones, but not so well from each other. They have a thin outer margin, 

 and their upper surface is marked by bands of irregular small fossee, and an 

 obtuse, longitudinal ridge. The middle line of the skull is occupied by the 

 supraoccipital. Its proximal portion probably separates the exoccipitals, 

 but this is not certain. It extends well forward, and the line of separation 

 from the frontal is not well defined. Its anterior part has a massive trans- 

 verse elevation, which sends a short median process backward, producing a 

 T-shaped body ; the frontal suture is probably in front of this. The supra- 

 occipital is contracted behind this body, and its postero-exterior suture pre- 

 sents a remarkable peculiarity in a straight and wide truncate articular 

 face. This is opposed by a corresponding face of the parietal bone; the 

 latter is of an irregular form, and carries on its outer portion next the pterotic 



* As suggested Proceed. Amer. Philos. Soc, 1872, p. 355. 



