The Gasteropoda, by Dr. J. Perner. 373 



above high-water mark, and the latter in the zone between high and 

 low water. Their characters are generally regarded as transitional, 

 and many authors would place them in the Opisthobranchiata rather 

 than in the Pulmonata. A full consideration of all the circumstances 

 renders it probable that the true relationship of Hercynella should be 

 sought elsewhere. Dr. Perner divides them into two groups, one 

 having low shells with a wide and but slightly raised fold, the other 

 composed of conical forms with a very prominent fold. Fifteen 

 species are recorded ranging from E-e 2, to G-g 3. 



The last order to be treated is the Heteropoda, Lam., to which 

 Dr. Perner refers two genera, Porcellia, Leveille, and Procarinaria, 

 gen. nov. ; the former to the family Atlantidse, and the latter to the 

 Pterotracheidae. He enters into minute particulars about the structure 

 of Porcellia, and gives his reasons for differing from other authors in 

 the position he assigns it. It is represented by six species, all from 

 E-e 2, with the exception of P. aberrans, Koken (/>. bohemica, Barr. 

 MS.), which is from F-f2. 



Procarinaria is created by Dr. Perner for the reception of a single 

 species from E-e 1. It is distinguished by a very small, compressed 

 shell whose aperture is slightly notched in the middle, and the keel 

 is solid and narrow. 



The description of species being thus completed, tables giving their 

 ranges follow. 



In Table i we have the genera arranged alphabetically, with their 

 synonymy, the species they comprise, their vertical distribution, and 

 references to their descriptions and figures. 



Table ii shows the vertical distribution of the genera arranged 

 zooloyically, with the number of species and particulai's about their 

 recurrence. 



Table iii contains the genera arranged alphabetically, with their 

 horizons and number of species. 



Table iv gives similar information for the families. 



Table v enumerates the genera and species occurring in each 

 ■ Bande ' into which the ' Etages ' are subdivided. 



The author's critical analysis of these tables gives, the general 

 results of his long labours and merits the closest attention. The total 

 number of species recorded is 719, of which 41 recur at different 

 horizons, they are comprised in 157 genera and 22 families. As 

 might be expected, the smallest number occurs in C (Cambrian), 

 there being but one family, the Patellidse, with one genus containing 

 two species. There is a considerable increase in Etage D, which has 

 29 genera comprising 69 species. 



E-e 2 contains the greatest number of species, viz. 406 referable 

 to 103 genera. 



E-e 1 has only 97 species included in 23 genera. 



F-f 1 shows a still further decrease, having only 1 1 genera containing 

 16 species. 



F-f 2 comes next to E-e 2 in numbers, having 147 species in 

 64 »enera. 



In G the amount of Gasteropoda decreases greatly, so that there 

 are only 13 genera with 19 species. 



