370 Dr. W. G. Ridewood on (he 



and Albulidee. They are undoubtedly primitive families, 

 and must have separated early from the common stock of 

 the Teleostcan fishes, hut one cannot regard the forward 

 intrusion of the trunk-muscles as aTiything but a charact;'r 

 of specialization which lias been j^enerated subsequently to 

 the severance of these families from the common stem. The 

 ancestral Elopids and Albulids were, of course, upon the line 

 of descent of the Gonorhyuchids, but the relationship is not 

 nearer. 



The Stoniiatidffi, in so far as they depart from the primi- 

 tive type, arc specialized in a direction contrary to that along 

 which Gonorhiinchus has become modified ; the well-developed 

 maxilla, formidable dentition, wide gill-opening, reduction 

 of opercular skeleton, and presence of a hyoid barbule in 

 the Storaiatidai indicate how futile it would be to search 

 for any evidence of close affinity between them and the 

 Gonorhynchidse. 



On comparing the skull of Gonorhynchas with that of 

 Cromeria there is to be noted a similarity in respect of the 

 rod-like form of the raetapterygoid and of the palatine (in 

 Gonurhyncltus the posterior portion only), the distinctness of 

 the angular from tlie articular bone, the failure of the first 

 basibranchial to ossify, the smallncss of the number of the 

 branchiostegal rays, and the narrowness of the gill-opening. 

 But against these resemblances there has to be set such a 

 large number of differences as suggests that the allies of 

 Gonorhynchus are not to be sought in the direction of the 

 Cromeriida;. Cromeria, for instance, has the frontal bones 

 widely separated, whereas in Gonor/rynchus they are so closely 

 united that the interfrontal suture is obliterated, it has no 

 ectopterygoid, no symplectic, no ascending process of the 

 paraspheuoid, no projecting snout, a single hypohyal on each 

 side, no epibranchial organ, a cartilaginous glossohyal, an 

 ossified fourth pharyngobranchial, and ossified fourth and 

 fifth basibranchials (see Swinuerton, Zool. Jahrb., Abth. 

 Anat. xviii. 1903, i)p. 58-70). 



Of the two remaining families which I propose to consider 

 — the Alepocephalidfe and Salmonidfe — the former is to a 

 certain extent specialized in relation with its deep-sea habits, 

 but in some respects remains more primitive than the latter. 

 It has no opisthotic, no teeth on the maxilla, an eye-muscle 

 canal closed behind''^, and an opercular bone very narrow in 



* In a cotiipnrison involving the SalinonicUB this character cannot be 

 allowed to cany much weiglu, since although the canal is open in such 



