1. AMPHIPNOUS. 13 



expanded, not leaving any non-ossified space between them. The 

 skull of Monopterus and Symhranchus is considerably elongate, the 

 entire branchial apparatus being below the skuU. It ia much 

 shorter in Amphipnous, in which only a part of the branchial appa- 

 ratus is below the skuU, the remainder being below the first four 

 vertebrae. The maxillary and intermaxillary bones run parallel 

 and are firmly attached to each other, the former extending further 

 backwards, but being toothless. The ethmoid is distinct as a sepa- 

 rate bone. The orbit is not marked by an osseous ring, its position 

 being indicated only by the foramen for the optic nerve. Palatine 

 bone extremely broad. The various opercular pieces can be clearly 

 distinguished. Each half of the humeral arch is composed of three 

 pieces, the lower (coracoid) being as usual the strongest and longest, 

 bent forward for the symphysis with its fellow ; the uppermost 

 (suprascapula) is very small and semicartilaginous in Ampldpnous, 

 continued into a muscle, which is attached to the skull, there being 

 no osseous connexion between the skull and humeral arch in 

 this genus. In Symbranchus and Monopterus this bone is well 

 developed, two-pronged, the upper prong being attached to the 

 occipital. 



There is also the greatest similarity of structure in the vertebral 

 column of the genera named ; the vertebrae are compressed, not 

 longer than deep. Their superior processes are slender, scarcely as 

 high as the centre of the vertebra ; no inferior processes ; the lateral 

 are perfectly horizontal, quite at the lower side of the vertebrae, con- 

 cave below, the processes of both sides forming together a concavity 

 like one-haK of a bivalve sheU. The caudal vertebrae are provided 

 with superior and inferior processes, which in Symbranchus and 

 Monopterus are dilated, lanceolate, and in Amphipnous styKform. In 

 all these fish the caudal portion of the vertebral column is much 

 shorter than the abdominal portion. To each of the transverse 

 processes a- short thin rib is attached. 



First Group. AMPHIPNOINA. 



i. AMPHIPNOUS. 



Amphipnous, Miiller. 

 Pneumabranchus, M'Clellnnd. 



Body covered with minute scales longitudinally arranged. Three 

 branchial arches, with the branchial laminae rudimentary, and with 

 narrow slits between them. A sac for the reception of air com- 

 municates with the gill-cavity. Gill-membrane nearly entirely 

 grown to the isthmus. Palatine teeth in a single series. 



Bengal. 



1. Amphipnous cuchia. 

 Dondoq Paum, Russell, pi. 35. 



Unibranchapertura cuchia, Ham. Buck, Fish. Ganq. pp. 16 363 

 pi. 10. fig. 4. ' 



