172 BATEACHIDiE. 



I have examined the foramen which is found in the axil of thia 

 species, and also of several others. It leads into a closed spacious 

 cavity, the inside of which is coated with a mucous membrane having 

 many reticulated folds. It appears to belong to the system of muci- 

 ferous channels, which is exceedingly developed in the fishes of this 

 family. 



The air-bladder is divided into two ovate lateral portions, com- 

 municating with each other by a narrow transverse tube ; the in- 

 ternal cavity is small, compared with the considerable size of the 

 organ ; this is due to the immense development of the muscle, fixed 

 to the side of each portion of the bladder. 



The genitals of the male show the peculiarity of two accessory 

 glandular organs being attached to the lower end of each of the 

 vasa deferentia. The one is compressed, externally similar to a 

 detached portion of the testicle ; the other, situated more inferiorly, 

 is of elliptical shape and of a blackish-brown colour. 



Skeleton. — The skull is distinguished by its depressed, broad, 

 rounded form, being similar in this respect to that of Coitus gohio or 

 Silurus glanis. The bones are well ossified, and the sutures gene- 

 rally very distinct. The crown of the skull is flat, twice as broad 

 as long, with the longitudinal crest scarcely visible, but emitting a 

 strong process joined to the neural spine of the first vertebra. The 

 posterior angles of the orbit are very prominent, and a transverse 

 muciferous channel, formed by two low ridges, runs from one angle 

 to the other. The orbital incisure is deep, sub-semicircular ; the 

 space between the orbits broad, flat ; a muciferous channel runs 

 along the orbital edge, and is bent inwards posteriorly to meet its 

 fellow from the other side (!/)• Praefrontal small, forming the 

 anterior angle of the orbit. The maxillary is long, slender, dilated 

 at the extremity ; the intermaxillary is much shorter, slightly di- 

 lated posteriorly, and with the posterior processes of moderate length. 

 The mandible is low, strong, and verj' long, strongly bent inwards 

 towards the symphysis ; its muciferous channels are Little developed. 

 The head of the vomer is very broad, flat, anteriorly with a denti- 

 gerous ridge ; palatine and pterygoid rather short and narrow. The 

 base of the cranium broad and quite flat. The epitympanic is large, 

 moveable, and so intercalated between the cranium, the operculum 

 and praeoperculum, that the two latter bones are rather remote from 

 the cranium. The praeoperculum is veiy solid, and larger than any 

 of the other opercular bones ; operculum reduced to three bony 

 radii, one of which is directed downwards ; the subopercxilum is a 

 thin subtriangular bone with a very strong ridge terminating in 

 a spine ; there are, besides, two much more feeble ridges above it. 

 Infraorbital bones none. 



The suprascapula and scapula are united into a single, long, 

 sword-shaped bone ; coracoid rib-like : the radius and ulna are very 

 short, whilst the carpal bones are elongated ; there are five of them, 

 the lower being the largest, the upper rudimentary. A very pecu- 

 liar styliform bone (a pair of transformed ribs) extends from the 



