GREGORY: FISH SKULLS 



353 



In conclusion the generally eel-like appearance of the Symbranchii, and the fact that 

 the parietals meet in the mid-line on top of the skull, together with the lack of fin spines, 

 have led most authors to place the order Symbranchii among the soft-rayed groups not far 



Cheilobranchus 



Fig. 232. Alabes. A. Cranium, top view. B. Left premaxilla and maxilla. C. Mandible. After Tate Regan. 



from the true eels. But Tate Regan after a more thorough consideration of the osteological 

 and other characters concludes (1912c, p. 387) that the "resemblances to the true eels are 

 not due to relationship" and that Alabes gives a clue to the derivation from some group 

 of acanthopterous physoclists, since Alabes possesses long ascending or articular processes 

 of the premaxillae, supraoccipital in broad contact with the frontals, triple occipital con- 

 dyles, jugular pelvic fins, etc. 



In Monopierus javanensis the otolith, according to Frost (1929a, p. 128), resembles t)iat 

 of Cepola Tubescens of the suborder Percoidea in general shape and in the sulcus. It differs 

 in certain details. The sulcus also resembles in its relative proportions those occurring in 

 Neobythites and Genypterus of the division Ophiiformes (suborder Blennioidea). In Sym- 

 branchus marmoratus the sagitta is ovate and apparently more specialized than that of 

 Monopterus (p. 128). 



Opisthomi (Mastacembelids) 



These "spiny-finned eels," or more properly eel-like spiny-fins, of Southern Asia and 

 Tropical Africa, show convergent resemblances to the eel-like dipnoan Proiopterus, since 

 the Indian Rhynchobdella aculeata, "conceals itself in the mud and becomes drowned in 

 water if unable to reach the surface, as it apparently requires to respire air directly" (Day, 

 quoted by Boulenger, 1910, p. 717). The dorsal fin is greatly elongate and is continuous 

 around the tail with the less elongate anal. The front half of the dorsal is represented by a 

 series of short detached spines. The ventral fins are absent. The head is very long and 

 narrow, the snout produced in front into a fleshy median tentacle bordered by the produced 

 tubular anterior nostrils, which lead into a tube that opens in front of the eye. The fishes 

 are carnivorous, with small eyes and hypertrophied olfactory chambers. 



The osteology of Mastacembelus has been described by Tate Regan (1912(f, pp. 217- 

 219), who figures the cranium. Our figure, however, is from the specimen. The cranium 

 is very elongate, more tapering in front, with very large long nasals covering the large nasal 



