76 



Cincinnati Society of Natural History. 



Union County, Tenn., a very sharply carinate variety with a 

 depressed spire. 



49. P. bryanti Harper. Station same as the last, also in 

 rotting leaves with brush. Since writing my notes No. 2, in 

 1 88 1, I have had opportunities to study this species carefully. 

 No doubt remains that it is as distinct from pcrspectiva as any 

 forms in the same genus could well be. 



50. Hclicodiscus lineatus Say. Found in leaves and occa- 

 sionally under rotting logs, bark, etc. The species is rare 

 here. It has close relationships with Patala, but is an 

 aberrant form which needs thorough study in connection 

 with the recognized divisions of Pyramidula. 



51. Pujictimi minutissimum Lea. Found, not rarely, in 

 leaves, together with many of the small species herein cited, 

 but not " on rotten or decaying wood in forests " so far as our 

 experience goes. The jaw of this species and other Poly- 

 placognatha is composed of numerous plates, either not 

 "soldered together" as in the present instance, or united by 

 membrane, or more or less over-lapping, and in various 

 degress of evolution toward the solid jaw or of retrocession 

 from it. In many species these plates are curiously differen- 

 tiated, some being bristle-bearing, others striate or minutely 

 tuberculate. It has been held by recent writers that these 

 characters are primitive, and indicate the antiquity of this 

 group. I believe it has been suggested that it may even be 

 a palaeozoic remnant. 



It may not be out of place to say in reply to this suggestion, 

 that the highly differentiated shells of the Polyplacognaiha , 

 and their equally highly unique jaw, do not seem to me to 

 indicate this vast antiquity, but rather that they are a group 

 of high degree, whether of great age or not. Had the shells 

 the size of the larger types of modern origin, they would be 

 the most striking objects that could be obtained among the 

 land mollusks. In support of this statement, attention is 

 called to the species of Laoma, Flammulina, etc. The isolated 

 geographical position of these latter groups is not suggestive 

 of high antiquity. 



52. Carychium exiguum Say. This shell occurs in great 

 numbers, in damp leaves, together with the other small 

 species herein enumerated. The variety found here is ex- 



