48 Messrs. Hancock & Howse 07i Janassa bituminosa 



preserved in the Dresden Museum was well figured in the 

 Dresden Magazine in the year 1762. Afterwards, in the year 

 1820, it was described by Schlotheim as a Trilobite, under the 

 name Trilohites hituminosus (Petrefactenkunde, p. 39) ; and in 

 1823 two figures were given by this author, in his ' Nachtrag* 

 ii. tab. 22. f. ^a,dh. 



Between the years 1833-1843, Count Munster figured and 

 described numerous examples of the strongly characterized 

 teeth and the shagreen skin of this peculiar fish under two or 

 three generic and five or six specific names. These teeth were 

 by him supposed to be palatal (an opinion which seems to be 

 entertained by later German authors), and to belong to a fish 

 of the Placoid order. After carefully examining the descrip- 

 tions and figures given by Count Munster, we fully agree with 

 those writers who consider that the following references belong 

 all to one species, and we also are quite assured that the speci- 

 mens obtained from the English Marl-slate are perfectly identi- 

 cal with those described by this author in his Beitriige zur Petre- 

 factenkunde : — Heft i. Janassa angulata^ p. 67, Taf. 4. f. 1, 2 ; 

 J. Humholdii, p. 122, Taf. 14. f. 4; /. bituminosa, Schloth. 

 p. 122. Heft iii. J. angulata, p. 122, Taf. 3 & 4. f. 5 a ,• Dictea 

 striata, p. 124, Taf. 3 & 4. f. 1, 3, 4 ; Taf. 8. f. 3, 4, 6, 7, 8, 9, 10. 

 Heft V. Janassa dictea, pp. 37-39, Taf. 15. f. 10-16. Byzenos 

 latipinnatus. Heft vi. p. 50, Taf. 1. f. 2. 



About the same time, Janassa was briefly described by 

 Agassiz under the name of Acrodus larva, Poiss. Foss. iii. 

 pp. 147, 174, 376, tab. 22. f. 23-25 ; and this learned author 

 for the first time pointed out the probable affinities of these 

 remarkable fish-remains. 



Later German authorities, and especially our friend Dr. 

 Geinitz, had already arrived at the conclusion that the va- 

 rious species of Janassa and Dictea described by Count Miin- 

 ster must all be brought back to one form, to which, by right 

 of priority, Schlotheim's specific name should be attached. 

 Indeed Dr. Geinitz has so recently (Dyas, 1861) examined 

 and carefully commented on the various species described by 

 Count Munster, that we think it better to give a translation 

 of his remarks than to offer detailed ones of our own, especi- 

 ally as Dr. Geinitz would have the advantage of seeing many 

 of the German specimens, and as we do not, excepting in one 

 or two points, differ in opinion from the conclusions arrived at 

 by this excellent naturalist. In fact Munster 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 

 hituminosa. Dr. Geinitz observes : — 



