50 Messrs. Hancock & Howse on Janassa bituminosa 



^' In our Janassa, the original of /. Humholdti, Miinster, all 

 the remaining teeth of the iirst cross row of the posterior divi- 

 sion, from the line a b, have an equal curvatm-e forwards of 

 their upper part. The teeth of the cross rows standing behind 

 them are only marked by broken roots. This specimen shows 

 yet another character of the genus Janassa, which has not yet 

 been described in any other specimen. At the posterior part 

 of the headj or rather at the entrance of the throat, there 

 are two large, similarly formed, bent teeth (dd), like all the 

 others of the posterior division, which Count Miinster took for 

 ear-bones (Beitr. i. 1843, p. 122). 



" On the specimens which are broken through parallel to the 

 palate-plate, as in ' Dyas,' tab. 5. f. 1, the six-sided form of 

 the teeth shows itself clearly ; but the boundary between the 

 anterior and posterior divisions of the teeth shows itself also 

 on these very distinctly, as the front teeth of the former have 

 the anterior side concave and the hinder convex ; but on the 

 latter this appears reversed {ib. tab. 5. f. 1 ) . In Miinster's figures 

 this relation is only taken into consideration in J. Dictea. 



" In our J. Ilumholdti (ib. tab. 4. f. 5) the first cross row of 

 teeth of the posterior division is by pressure driven close to 

 the last cross row of the anterior division, and partly under it, 

 for which reason one cannot see the separating furrow ; and 

 Count Miinster has felt himself justified in placing J. Hum- 

 boldti with Dictea (Beitr. v. p. 38). 



'' From the similar form of the teeth of Miinster's Janassa and 

 Dictea, of which the structure is always tubular, while the 

 outer surface of the root shows more or less distinct transverse 

 roots (Dyas, tab. 4. f. 5, c, and tab. 5. f. 1), and from the perfectly 

 similar arrangement of the teeth in J. angulata, J. Dictea, and 

 J. Humboldti, Miinster, with that in our figures, which cannot 

 be recognized in Miinster's ideal and quite incorrect figure 

 (Beitr. iii. tab. 3 & 4. f. 2), there can exist no doubt Avhatever 

 as to the identity of both genera and the five different species 

 in them. 



^' In Dictea striata, Miinster (Beitr. iii. tab. 3 & 4. f.l), the 

 whole contour of the fish appears before us, though the swim- 

 ming-appendages which surround the body permit a different ex- 

 planation, because this specimen lies more on the belly. The 

 length of the fish, Avithout the caudal fin, is 0*390 metre ; the 

 height of the head 0'080 metre, the body at the pectorals, 

 not including these, 0*071 metre ; the greatest width between 

 the ventrals and the pectorals O'llO metre, at the anal fin 

 0*055 metre, and at the base of the tail 0*035 metre broad. 

 The whole body and all the fins or swimming-enlargements 

 are covered with a fine shagreen skin. 



