338 GEOLOGICAL SUEVEY OF THE TEEEITORIES. 



parative anatomy, and also to tlie paleontologist, as they appear to 

 have been the predominant type of marine fishes during the Cretaceous 

 period in the North American seas, and to have been abundant in those 

 of Europe. 



The characters already assigned to the family are confirmed by the 

 new species discovered, and many additional ones added, as follows : 



The cranial structure cannot be fully made out, but the following 

 points may bS regarded as ascertained. The brain-case is not continued 

 between the orbits, and the basis cranii is double and with the muscular 

 tube open. A large cavity is inclosed by the prootic, the pterotic, the 

 opisthotic, &c. There are no exoccipital condyles, and that of the basio- 

 occipital is a conic cup. The pterotic and post-frontal are well devel- 

 oped. The ethmoid is well developed and slightly narrowed at its an- 

 terior extremity. The paraspheuoid is narrowed and elongate; the 

 vomer is continuou.i with it and is slightly expanded and then con- 

 tracted at the anterior extremity. Is'either it nor the parasphenoid sup- 

 I)ort teeth in any of the known genera. 



The premaxillary bones are short, and form but a small portion of the 

 upper jaw. The maxillary is elongate and simple. The hyomandibu- 

 lar is rather narrow and does not present an elongate support for the 

 operculum. The symplectic is well developed, entering far into the 

 inferior quadrate. The latter is a broad bone, large, in contact with the 

 metapterygoid, which is itself a thin plate, not probably attaining the 

 pterotic. The superior branchihyals are short rods. 



The relations of the supraoccipital, j)arietals, frontals, &c., cannot yet 

 be satisfactorily made out, owing to the obscurity of the sutures. Never- 

 theless, the following points may be regarded as probably reliable. The 

 frontals have a rather broad union with the ethmoid, and are separated 

 by suture throughout their length. They do not extend much posterior 

 to the orbits, and are succeeded by a rather narrow pair of bones, which 

 extend to above the foramen magnum. These are not united by suture, 

 but present thickened, smooth edges to each other, and appear, tbere- 

 fore, to have been separated by a fontanelle. Each is separated from a 

 broad, lateral bone by a serrate suture, which is, perhaps, the pterotic, 

 and certainly includes that element, as it supports the hyomandibular. 

 It is not easy to determine what relation the median bones bear to the 

 supraoccipital, but the structure looks a good deal like that character- 

 izing the Siluridw, or, considering the large j)terotics, like the Mormy- 

 ridw plus the fontanelle. The shorter form of the pterotic in the 

 Characinidm an'd the Catostomidw causes considerable difference in their 

 appearance. There is no indication of fontanelle between the frontals 

 in Fortheus. 



Portions of the scapula of Fortheus molossus and other species are 

 preserved. They have very stout articular surfaces, and, although not 

 complete, have enclosed, more or less, a very large fontanelle. The 

 superior surface is the larger, and is followed below by two others ; the 

 upper subvertical and small, the lower larger and transverse. These are 

 surfaces supporting two basilar elements of the pectoral fin. There 

 were, perhaps, three basilars ; but the base of the coracoid displays no 

 surface for articulation of a third. 



The suture with the coracoid crosses immediately below the lower 

 condyloid surface, and passes just below the scapular fontanelle, leaving 

 in the specimens a fractured surface, which probably supported a prse- 

 coracoid. There are two fractured bases of the coracoid, which proba- 

 bly unite below, enclosing a foramen. On the scapulo-coracoid suture, 

 just within , the space between the two inferior condyles, is a smooth 



