ON JANASSA BITUMINOSA. 341 



Ib fact, Miinster himself seems to have been satisfied that his 

 genera Janassa and Dictea were identical, and also to have had 

 some doubts as to the value of some of the species which he has 

 made of Janassa bituminosa. Dr. Geinitz observes : — 



" The beautiful original of J. Humbolclti in the Dresden Mu- 

 seum (Dyas, tab. 4, f. 5), of which a very good figure was given 

 in the year 1762 in the 'Dresden Magazine,' and which happily 

 was recovered from the ashes of the fire at the Zwinger, is again 

 figured here, because Miinster' s figure is reversed. This still 

 beautiful specimen deserves a new illustration because it fur- 

 nishes a proof, that not only all Count Miinster' s species of 

 Janassa, but also his Dictea striata, must be referred to the type 

 to which the first name given by Sehlotheim belongs. 



" The oval, uniformly arched palate (Gaumen) is paved with 

 from five to seven rows of chisel-formed, strongly curved at their 

 upper enamelled end, and nail-shaped recurved teeth, which are 

 indistinctly imbricated, and which are separated by a deep fur- 

 row into an anterior and a posterior division. 



"In the teeth of the anterior division the nail-formed end is 

 bent backwards to the throat (ib. tab. 5, f. 3), in those of the 

 posterior, on the contrary, forwards {ib. tab. 5, fig. 4). The three 

 middle rows of the anterior division, of which each one has six 

 teeth, the size of which increases from before backwards, contain 

 generally the largest teeth : only these three rows have been 

 figured by Sehlotheim, who thought he saw in them the struc- 

 ture of the Trilobites. On each side lie two more rows of smaller 

 teeth, which stand obliquely to the primary rows, and of which 

 the outer ones only appear to be lamelliform.* They are not 

 shown in Miinster's figure of J. angulata (Beitr. i. tab. 4, f. 1, 2). 

 In Beitr. iii. tab. 3 & 4, f. 5, they are only partly to be seen ; 

 but on the J. Humboldti they are better shown, while in Miin- 

 ster's J. Dictea (Beitr. v. tab. 15, f. 10) they stand a little sepa- 

 rated, certainly from the result of dislocation. 



"The posterior shorter group of teeth, which in Miinster's 

 figure (Beitr. v. tab. 15, f. 10) is represented as correctly as 

 possible, contains as many longitudinal rows of teeth as the 



* The lamclliform teeth of Geinitz are those we have named pctrlodontoid. 



