"""isao'."'] PROCEEDINGS OF THE NATIONAL MUSEUM. 241 



Mouth with the cleft transverse aud slightly exteudiug laterally back- 

 wards. 



Jaws very stout; maxillincs approximated to the frout of the aiiteal, 

 with the claspiug processes narrow, selliforni, and appressed closely and 

 obliquely to the sides of the auteal behind its head ; each has a broad, 

 ledge-like extension extending obliquely upwards within along most of 

 the length, and behind expanding downwards into a cleaver-sh;iped 

 process obliquely truncated behind ; mandible with the rami very stout, 

 and deep, each dentary has the coronoid process well developed, and 

 the inferior edge is strongly bowed downwards ; articular extending for- 

 wards on the outer surface of the mandible scarcely in advance of the 

 condyle. 



Teeth bkint, uuiserial, on the edge of the jaws and acrodout. 



Li])s completely suppressed. 



Tongue large, filling the whole floor of the mouth, with its margin free 

 and bevelled, having a trenchant upi)er edge. 



Periorbital bones almost membranous. 



Opercular apparatus peculiarly developed ; operculum falciform, in- 

 serted nearly midways on the hyomandibular and decurved downwards 

 and then upwards in harmony with the branchiostegal rays ; suhoper- 

 culum below and parallel with the oi)erculum ; inter operculum lamelli- 

 form and widened upwards towards its junction with the operculum; 

 preoperculum well developed and closely ai)pressed to the suspensorium. 



Branchiotremes inferior and manifest as longitudinal slits moderately 

 distant from each other. 



Branchiostegals in reduced number (8-9), moderately stout and partly 

 widening towards their enik;, long, and recurved over the operculum. 



Dorsal, anal, and caudal confluent into an uninterrupted fin, with the 

 rays readily perceptible through the skin ; ^Zor6«i commencing not very 

 far behind the head; anal close behind the anus; caudal prominent 

 backwards. 



Pectorals well developed, near the breast and with narrow bases and 

 median branched rays. 



Branchial arches nearly complete, with a styliforin glossohyal and a 

 much abbreviated urohyal, and with the first and second basibranchials 

 ossified; first and second hypobranchials ossified; third cartilaginous; 

 fourth suppressed ; ceratobranchials and epibranchials of four pairs 

 ossified; pharyngobranchials of three (?) i)airs connected with epibran- 

 chials; those of the last pair developed as thin dentigerous epipharyn- 

 geals dislocated towards the ceratobranchials; hypopharyngeals with 

 narrow dentigerous surfaces aud closely appressed to the fifth branchial 

 arch.* 



* The branchial apparatus described is imperfect aud the description may possibly 

 be defective or erroneous. 



Proc. i^. M. 90 16 



