BRUSTNA : PAPYROTHECA, A NEW GENUS OF GASTROPODA. l6l 



I have sent a few specimens to the distinguished conchologists 

 M. Cossmann, of Paris, and Dr. O. Boettger, of Frankfurt am Main. 

 The first wrote me : " Papyrotheca mirabilis ressemblerait a un 

 Pteropode, si le sommet n'etant pas tordu comme dans quelques 

 genres de Gasteropodes ; c'est tout a fait curieux et vraiment mirabilis!'' 



Dr. Boettger wrote very strikingly: "Your Papyrotheca is very 

 singular. As it is for certain a freshwater snail any relationship with 

 the Succinea, Omalonyx, &c, disappears. Considering the thinness 

 of the shell the existence of an operculum is likewise impossible, 

 therefore a comparison with Navicella is also out of the question. 

 There remains, consequently, but the Limnceidce, and here the 

 position between Latia and Limncea, in my opinion, is acceptable, 

 even though any living or fossil analogues are unknown to me." 



Special Part. 

 Papyrotheca, gen. nov. 



The shell is very frail, as if made from a slip of white paper, 

 hardly whorled and not umbilicated, consisting of the apex and one 

 volution. The form is a very peculiar one, and it can only be 

 compared with a depressed Succinea that has adapted the form of a 

 lengthened Crepidula. The apex is smooth, elongated like Acei/a, 

 and makes but a single turn (PI. II., fig. 3) ; which at once widens 

 into a very broad mouth, this latter forming nearly the whole of the 

 shell, and having no lips, the edges being sharp. The spindle-shaped 

 edge which is developed directly under the apex and runs towards 

 the mouth, forms a comparatively large lamella ; this forms a rather 

 acute angle with the hinder portion of the mouth. The external edge 

 of the mouth is largely extended below, simple, but above opens into 

 an acute angle, and therefore forms a septum-like lamella. This 

 reaches the already described lamella on the spindle-shaped edge, 

 unites with it, but only partly covers it, often leaving a distinct flat 

 space, not unlike a deepened grove. 



The shell has rather the appearance of a mussel, for it shows fine 

 concentric, not quite regular stria? which show more on the back, 

 while the interior of the shell is nearly smooth. 



Papyrotheca mirabilis, sp. nov. 

 (PI. n, figs. 1-3.) 



To the description of the genus, we have only to add that the 

 spindle plate of this species is very narrow, but the external plate — 

 or as I have previously termed it, the septum — is very broad, and its 

 surface is marked with a large number of fine and fairly regular 

 wrinkles. The edge of the septum is crescentric. 



