32 DEEP SEA FISHES. 



has rather large spiracles, a smaller anterior dorsal situated behind the 

 pectoral fins, a larger second dorsal tlie base of which is in part above the 

 bases of the ventrals, a body chamber nearly two thirds of the total length, 

 a deep and comparatively short caudal, and a black ventral surftice; 

 Eafinesque described and figured his type as having no spiracles, a large 

 anterior dorsal above the pectoral fins, a small second dorsal " quasi 

 adiposa," ventrals far in advance of the second dorsal, a body cavity less 

 than half of the total length, an elongate narrow caudal, and white lower 

 surfaces. Even if Rafinesque's Dalatias should be re-discovered it would 

 be excluded from the present family by the characters given : Nessuno 

 Spiraglio, due ale dorsali, senza ala anale, cinque aperture branchiali da 

 ogni lato, coda disuguale obbliqua — Oss. Questo genere di Sqimlini 

 differisce dal genere Carcharias per la mancanza dell' ala anale e da quello 

 del Squalus per quella degli Spiragli." The names Ddatiana and Dalatias 

 lichia of Gray, 1851, owe their existence to guesswork identification with 

 Rafinesque's problematical species. The fact that Scymnorhinus inhabits 

 the greater depths accounts for the scareity of representatives in the 

 museum collections. While its distribution has not been determined be- 

 yond the European seas it will probably be much extended by future 

 research. Special interest is attached to the family, in this report, on 

 account of the presence in the collection made by the "Albatross" of one of 

 the closest allies of Scijmnorliinus, of a genus of much wider known distribu- 

 tion and possessed of characters which in some respects are more than 

 sufficient for generic distinction, as may be seen in the following diagnoses. 

 The family may be subdivided thus : 



Dorsals unlike ; anterior smaller, in advance of the middle of the length ; 

 lower teeth with serrate edges ; scales with an acute cusp or trowel shaped 

 — Scymnorhinidcc. 



Dorsals similar, nearly equal; anterior behind the middle; lower teeth 

 with smooth edges; scales in pavement, without regular cusps — Jsistiidce. 



ISISTIID.E. 



This group is based upon a small shark which is readily distinguished 

 from the Scymnorhinidce proper by the backward position of the first dorsal, 

 the tile-shaped polygonal scales, the absence of serrations on the cutting 

 edges of the lower teeth, and the presence of a dermal keel at each side of 



