32 DEEP SEA FISHES. 
has rather large spiracles, a smaller anterior dorsal situated behind the 
pectoral fins, a larger second dorsal the 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 surface; 
Rafinesque 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 Sgualini 
differisce dal genere Carcharias per la mancanza dell’ ala anale e da quello 
del Squalus per quella degli Spiragli.’ The names Dalatiana and Dalatias 
lichia of Gray, 1851, owe their existence to guesswork identification with 
Rafinesque’s problematical species. The fact that Sceymnorhinus inhabits 
the greater depths accounts for the scarcity 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 Seymnorhinus, 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 
— Scymnorhinide. 
Dorsals similar, nearly equal; anterior behind the middle; lower teeth 
with smooth edges; scales in pavement, without regular cusps — Lsistide. 
ISISTID. 
This group is based upon a small shark which is readily distinguished 
from the Scymnorhinide 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 
