244 LILLJEBORG ON THE 



nearly of the same lengtli as the haiclcr part of the bead. The symphysis of the two lower jaw- 

 bones is quite short, much shorter than half the length of the bones. It seems to approach the 

 next preceding also in regard to the rest of the skeleton, and has only 2 or 3 vertebræ more. 

 Only one species of this genus is known, belonging to the northern Polar sea. 



M. MoNocEKOS, Lin. The Narwhal. SioeiUsh " Narhval." 



Monodon monoceros, Linné. Fauna Suecica, p. 16. 



— (). Fabricius. Faima Groenlandica, p. 29. 



Des Nauvals, G. Cuvier. Recherclies sur les Osseraens Fossiles, t. v., l"'" partie, 



p. 319, tab. xxii, fig. 7. 

 MoNODON .MONocEROs, F. Cuviev. L. c, p. 230, tab. xvii, figs. 2 and 3. 



— — J. A. Wac/ner. L. c, p. 267, tab. cccxxx. 



— — S. Nilsson. L. c, p. 619. 



Length 12' — .20', exclusive of tusk, which is 0' — 10' long. In general form the body seems 

 to be less thick than that of the next preceding. It has, like that, a longitudinal protuberance on 

 the back, about the middle of the body, as a rudiment of a dorsal fin. The body is thickest at the 

 foremost part of the protuberance ; it tapers backwards, and is, near the caudal fin, considerably 

 compressed, with sharp edges above and below, although to not quite the same extent as in 

 the preceding species. Scoresby (according to J. A. Wagner) gives the following measure- 

 ments of a male: — Length of body, exclusive of tusk, 15' (English). Circumference at the 

 beginning of the protuberance on the back 8' 5". Distance from nose to anus 9' 9". Pectoral 

 fins 13" long and Tj" wide. Caudal fin 3' V!' wide. Tusk, external to the jaw^ 5' j". The 

 colom- of grown specimens is, according to Scoresby, white, or yellowish-white, with grey or dark- 

 brown spots. The young, when quite small, are said to be bluish-grey or dark grey;^ when 

 somewhat larger they are, above, black ; beneath and on the sides spotted with grey and white. 



Tlie length of the beak of the skull is about 1^ its width at the base. The intermaxillary 

 bones, on the upper side of the beak, are about as wide as the superior maxillary, at their 

 outer side. The intermaxillary bones and the nares are directed posteriorly somewhat to the 

 left. The right intermaxillary bone extends somewhat further back than the left one, neither of 

 them touching the nasal bone. The skull of a full-grown specimen is about 2' long and 16" 

 wide (S. Nilsson). The long and sharp tusk, which is generally in the left side of the upper jaw, 

 is spiral to the left, or has on its surface spiral ridges or protuberances running to the left. The 

 spiral ridges run to the left, even \vhen the tusk is in the right side of the upper jaw. It is 

 hollow to near the point, and has a persistent pulp in this cavity. Its alveolus is about 14" 

 long, and extends somewhat behind the lateral notch of the superior maxillary, or about to the 

 orbits. The diameter at its base is about 4", when its length is 9' or 10' (Owen). The tusk is 

 nearly 6' long from its base in a skeleton H4' long, in the Zoological Museum in Lund. This 

 skeleton has 1 2 dorsal vertebræ, 9 lumbo-sacral, and 2 5 caudal, 1 6 of which carried processus .spinosi 



^ This seems to be the colour to which Fabricius refers, in stating : " Colore totus niger." 



