408 MONOGRAPH OF THE AUSTRALIAN MARSIPOBRANCHIT, 



Body elongate and slender, strongly compressed; head moderate, 

 oblong, attenuated and depressed, with narrow rounded snout; 

 suctorial disk small, oval, subinferioi', extending backwards about 

 midway to the orbital region, with a smooth free outer lip, along 

 the inner border of which a regular series of short, simple, dis- 

 tant papillfe is inserted anteriorly and laterally; on the rim of the 

 disk is a second series of broad, profusely fringed, foliaceous 

 papillae, which is continued entii^ely round the hinder margin of 

 the disk where it is widely separated from the external lip; 

 surface of disk traversed by numerous series of closely set 

 cutaneous ridges arranged more or less obliquely. No gular 

 pouch. Branchial orifices moderate and slit-like, with distinct 

 functional valves in front and behind, the latter fringed. 

 Maxillary dentition consisting of a single transverse, crescentic, 

 quadricuspid plate, the outer cusps being smooth and much 

 larger than the inner pair, their extremities entire; mandibular 

 plate low and crescentic, strongly cuspidate; disk with an inner 

 series of moderate, diversely shaped teeth, from the bases of 

 which radiate series of small, contiguous, graduated teeth, which 

 are embedded in the hinder margin of the discal ridges; no sub- 

 sidiary teeth behind the mandibular lamina ; tongue with a 

 single large plate, smooth on its outer, tricuspid on its 

 inner margin, along either side of its dorsal surface; below 

 with a strong, transverse, basal plate, provided with three 

 (sometimes two*), slender acute cusps directed forwards. 

 Two well developed dorsal fins, the anterior inserted far behind 

 the middle of the body, the posterior much the larger and 

 separated from the caudal by a moderate interspace; caudal fin 

 well developed, continued around the extremity of the tail by a 

 low, rayed membrane. Tail long, the vent situated below the 

 origin of the second dorsal fin. Head with series of small, open 

 pores; a series of widely separated pores along the middle of the 

 trunk and along the bases of the fins. 



*When the median cusp is abseat the retnaiaing two are widely separated 

 at the base, not contiguous as in Geotria. 



