516 



Nachdruck verboten. 



On Certain Features of the Anatomy of Siren lacertina. 



By H. W. NoRRis, Grinnell College, Grinnell, loAva, U.S.A. 



In connection with a study of the distribution of the cranial 

 nerves of Siren, the results of which will be published in the near 

 future, the writer found certain features of the general anatomy that 

 seem worth especial notice. 



Vaillant (1863) in describing the muscles of the head in Siren, 

 mentions "I'abducteur de la machoire superieure", a small muscle 

 said to be inserted in part upon a small bone believed by Cuviee to 

 be a maxilla. The writer has not had access to this paper on Siren 

 by CuviER, but has made use of the reproduction of his figures by 

 Hoffmann (1878). Fischer (1864), Wiedersheim (1877) and Wilder 

 (1891) have not been able to find either the muscle mentioned by 

 CuviER and Vaillant or the small bone on which it was said to be 

 inserted. Parker (1882) mentions and figures two "small seed- like 

 centers opposite the middle of the premaxillaries " as maxillaries, but 

 he says nothing of muscles connected with them. The writer finds 

 in the position described by Parker a minute ossification on each 

 side. This may, however, be larger on one side than on the other, 

 in fact is wanting altogether on one side in some specimens. Its 

 minute size, and possibly complete absence on both sides in some 

 instances, may explain the failure of some investigators to find it. 

 It has no muscles connected with it. It probably represents a maxilla, 

 as CuviER, Vaillant and Parker believed. 



In the lower jaw of Siren Wiedersheim describes three skeletal 

 elements, dentale, angulare and meckel's cartilage. Huxley (1878) 

 mentions "a dentigerous splenial element". Parker describes a sple- 

 nial as "a very delicate, styliform, dentigerous splint". Gadow (1901) 

 recognizes a splenial in Siren, but says that "with the exception of 

 small teeth on the vomer the mouth is toothless". The writer finds 

 the operculare (spleniale) as described and figured by Parker, and 

 formed chiefly by the fusion of the bases of teeth. 



