LA MPRIDI FORMES 



477 



half-way up the body, and the anal fin has been lost. The caudal fin 

 has disappeared in Begalecus, but in Trachypterus is strangely modified, 

 the dermal rays being separated into two diverging fascicles (Fig. 506). 



Trachypterus, Gouan (Fig. 506), and Begalecus, Briinn (Fig. 505)— 

 widely distributed. 



Fie. 506. 

 /' hypterus tat nia, Schn. (After Gtinthe.r.) 



Family Stylephoridae. The deep-sea genus Stylephorus is very 

 much specialised, having lost the pelvic fins, the arches of the vertebral 

 column, the orbitosphenoid, and the greater part of the pterygopalatine 

 bar. The ceratohyals are widely separated below, the ethmoid is carried 

 by the parasphenoid far from the vomer, and the lower jaw has acquired 

 a huge size in spite of the presence of a very small tubular mouth 

 (Stark s). 



Stylephorus, Shaw ; Pacific. 



Division 4. MASTACEMBELIFORMES ^Opisthomh. 



A small group of Acanthopterygian fishes which have acquired 

 a deceptive resemblance to the Eels, not only in outward shape but 

 also in internal structure. The body is elongate, the tail gephyro- 

 cercal, the long dorsal and anal fins confluent at its tip ; the snout 

 is prolonged as a pointed movable appendage ; the pelvic fins have 

 been lost. The dorsal fin is continued forwards as a series of 

 detached spines, and spines are also present in the anal fin. The 

 scales are very small. The nostril is single on each side, the non- 

 protractile mouth is bordered by the premaxillae. The panetals 

 are separated by the supraoccipital which joins the frontals ; and 

 the pectoral girdle is attached, not to the skull, but to the vertebral 

 column. The numerous trunk vertebrae bear transverse processes 

 and ribs. The air-bladder is closed. These -fish are adapted to 

 air-breathing, the branchial opening being small and ventral. 



