

true: the type of anoplonassa forcipata 99 



The chief features of the mandible of Anoplonassa are as follows : 

 (1) Its slenderness ; (2) the slight depth of the symphysis in proportion 

 to its length, and the strong convexity of its sides ; (3) the upturned 

 and expanded termination ; (4) the pair of large, nearly round, and very 

 slightly depressed terminal alveoli ; (5) the rudimentary alveolar groove, 

 with its pair of rather small and shallow elliptical alveoli, not far distant 

 from the terminal pair ; (6) the large size and peculiar disposition of 

 the inferior terminal foramina. 



It is a well-known fact that in Mesoplodon and other existing genera 

 of ziphioids, the superior alveolar border of the mandible in -young indi- 

 viduals, at least, presents a shallow, more or less rudimentary, alveolar 

 groove, and that in a certain proportion of specimens there are, in addi- 

 tion to the 2 or 4 large teeth, a number of very small, rudimentary 

 teeth, which are imbedded in the integuments, and rest on, or partly in, 

 the groove. 



The groove itself occupies rather more than the anterior half of the 

 superior border of the mandible. In Mesoplodon it is interrupted by 

 the deep alveoli of the single pair of large teeth, which in most species 

 are at a considerable distance from the anterior end of the mandible. In 

 young specimens of Berardius, a genus with four large teeth, the inter- 

 space between the anterior tooth and the posterior tooth on each side is 

 extremely small, and the rudimentary alveolar groove really begins behind 

 the posterior tooth. In adults, however, the diastema between the anterior 

 and posterior deep alveoli may be as much as 70 mm. This interspace 

 is not depressed, but is rough and pierced by several canals. 



In a mandible of Ziphius cavirostris 770 mm. long, the alveolar groove 

 has a maximum width of about 9 mm. and a maximum depth of about 5 

 mm. In another imperfect mandible of Ziphius from an old individual 

 the groove is deeper, especially anteriorly. The maximum depth is 

 about 11 mm. In all the ziphioid mandibles examined, the groove is 

 the broadest at the anterior and posterior ends. The floor of the 

 groove is very uneven, and is pierced by numerous foramina for nutrient 

 vessels and nerves. The edges of the groove in some specimens are quite 

 smooth and straight. In others they are more or less crenulate, produc- 

 ing here and there the appearance of genuine alveoli, but these depres- 

 sions never have the depth or the regular form of the alveoli of the large 

 teeth. 



The groove above described is found in Anoplonassa, with a similar gen- 

 eral conformation and relative size. The walls, however, are more strongly 

 crenulate than in specimens of existing ziphioids I have examined. 



