Families of Teleostean Fishes. 171 



from the frontals by the parietals, which form a long median 

 suture. This is a feature which has only been observed in 

 fishes with abdominal ventral fins ; and although the total 

 absence of these fins in Fierasfer deprives us of an important 

 criteiion in deciding on its affinities, I am inclined to regard 

 this family as derived from an abdominal type. The con- 

 formation of the pectoral arch has much in common with 

 that of the Halosaurs, and, notwithstanding the interpretation 

 that has been given to the bones at the back of the cranium 

 in the latter type, the same may be said in a general way of 

 the skull. 



As pointed out by Emery, the very anterior position of the 

 vent in the Fierasferidpe is directly related to the curious mode 

 of life of these fishes, and the analogous condition obtained in 

 various families, such as the Gymnarchida?, Nemichthyiclse, 

 Amblyopsidse, and Aphredoderidae, shows it to be of relatively 

 small importance. 



Five families : — 



Ordinary scales small or wanting, but two or more 



continuous series of enlarged scutes along each 



side ; mouth large, pmemaxillaries apparently 



forming the greater part of the upper border of 



the mouth, which is toothed ; opercular appa- 

 ratus complete ; dorsal tin more or less extended, 



without spines ; anal short ; caudal separate ; 



ventrals with not less than 7 or 8 rays 1. Dercetida; f. 



Body covered with cycloid scales, the tail tapering to 



a point, without caudal fin ; head with scales ; 



mouth moderate, bordered by the prsemaxillaries 



and the maxillaries, both toothed; suborbitals 



large ; prseopercle rudimentary ; dorsal fin short, 



without spines ; ventrals formed of 9 or 10 soft 



rays ; anal very long, without spines, extending 



to the end of the tail 2. Halosauridce. 



Similar to the preceding, but with a toothless, round- 

 ish inferior mouth and with the short dorsal and 



the long anal formed partly of spines and partly 



of soft rays ; ventrals with 3 spines and 7 soft 



rays 3. Lipogenyidee, 



Body covered with cycloid scales, the tail tapering to 



a point, without caudal tin ; head with scales ; 



mouth small, inferior, bordered by the praemax- 



illaries only ; jaws toothed ; no suborbitals ; prae- 



operculum small ; post-temporal replaced by 



ligament; dorsal fin formed of a series of short 



disconnected spines : anal very long, formed 



partly of spines aud partly of soft rays ; ventrals 



with 1 to 5 spines and 7 to 10 soft rays 4. Notacanthidce. 



Body extremely attenuate, naked ; no caudal fin; 



mouth small, inferior, bordered by the praemax- 



