528 DR. J. E. GRAY ON CETACEA [June 27, 
PETRORHYNCHUS CAPENSIS. 
Hyperoodon capensis, Gray, P. Z.S. 1865, p. 359. 
Hab. Cape Seas. 
The skull of this Whale resembles in several particulars the skull 
of Ziphius cavirostris, figured by Gervais (Zool. et Paléont. Frang. 
t. 39); but the cavity on the crown of that species is only slightly 
developed, though it is apparently rather more developed in the other 
specimens figured on the plate (t. 38. f. 1, 2) of that work ; and the 
vomer is sunk in a groove as in the other Ziphioid genera, except in 
the specimen figured at t. 38. f. 2, which has the most developed 
frontal cavity, and in this there is an appearance as if the vomer was 
larger. 
Phe study of this skull and of the Ziphius described by M. Van 
Beneden, received from the Cape, has induced me to reconsider the 
arrangement of the genera of Ziphioid Whales, which I have formed 
into a family, Ziphiide, which may be thus characterized :— 
Head beaked ; blower linear, transverse, on the back of the head. 
The upper jaw toothless, or with a few rudimentary teeth, which are 
not or only rarely developed. Lower jaw with a few teeth on the 
side or in front, which are sometimes early deciduous or not exposed. 
Body elongate ; dorsal fin faleate ; pectoral fins small, low down, and 
rather close together on the middle of the chest ; fingers five, of four 
or five phalanges. Skull with an enlarged nasal over the blowers, 
which are more or less sunken. 
This family may be divided into three sections. 
1. Hyperoopontina. Teeth in front of the lower jaw conical. 
Beak with a high crest on each side, formed by the elevation of 
the maxillary bones. 
Hyrreroopon. Beak of skull straight ; crest of beak short, edged, 
only as high as occiput. H. butzkop/f. 
Lacenocetus. Beak of skull ascending; crest of beak flat, 
tipped, higher than the occiput. L. latifrons. 
2. Erropontina. Teeth in front of lower jaw cylindrical or conical. 
Beak conical ; the intermazillary enlarged behind, forming a 
more or less large cavity round the blowers. 
ALiAMA. Vomer simple; intermaxillary only slightly elevated 
on the sides of the blower. Teeth large. A. indica=Ziphius in- 
dicus, Van Beneden. Cape of Good Hope. 
Erropon. Vomer forming a sunken groove ; intermaxillary form- 
ing a moderately high basin round the blower. H. desmarestu= 
Ziphius cavirostris, Cuvier. Mediterranean. 
Perroruyncuus. Vomer swollen, forming a large elongated 
tubercle between the callous intermaxillary ; intermaxillary form- 
ing a high basin round the blower. P. capensis. Cape of Good 
Hope. 
