from the Marl- Slate of Midderidge. 49 



" Tlie beautiful original of J. Ilumholdti in the Dresden 

 Museum (Djas, tab. 4. f. 5), of which a verj good figure was 

 given in the year 1762 in the ' Dresden Magazine/ and whicli 

 happily was recovered from the ashes of the fire at the Zwinger, 

 is again figured here, because Mlinster's figure is reversed. This 

 still beautiful specimen deserves a new illustration, because it 

 furnishes 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 Schlotheim 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 furrow into an anterior and a posterior division. 



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

 bent backwards to the throat [ih. 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 Schlotheim, avIio thought he saw in 

 them the structure 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 Mlinster's figure of J. 

 angidata (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. Humholdti 

 they are better shown, while in JMiinster's J. Dictea (Beitr. v. 

 tab. 15. f.. 10) they stand a little separated, 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 an- 

 terior division,^ which in size decrease backwards and stand in 

 five transverse rows. Their upper enamelled end seems in all 

 to be bent forwards, or in the opposite direction to those of 

 the anterior group of teeth. Miinster ascribes such a curva- 

 ture to two teeth only, which in his specimen are situated im- 

 mediately between the two divisions of the palate and out of 

 place (Beitr. v. p. 39, tab. 15. f. 13, /7, h) ; but he announces 

 expressly that this palate is a little drawn out and dislocated, 

 for which reason the teeth are not in their usual regidar 

 position. 



* The lamelliform teeth of Geinitz are those we hare named petalo- 

 dontoid. 



Ann. d; Mag. N. Hist. Ser.4. TV. v. 4 



