426 



The preceding three species form a peculiar group near to 

 Cyclostoma proper, characterized by the thin paucispiral opercle 

 with thinned edges, the globose conic form, free umbilicus, nearly 

 circular peristome which barely touches the preceding Avliorl, and 

 the projecting lamellar striai of growth decussating with revolv- 

 ing ridges in some cases furnished with epidermal barbs. It 

 may be called Japonia. 



Helicina verecunda. T. pyraraidato-lenticularis, spiraliter 

 minutissime striata, luteo-virens ad apicem rubescens, ad peri- 

 pheriam subangulata, subtus convexa, admodum callosa ; anfr. 

 4 planulatis. Apertura ovato-triangularis ; peristomate evaso, 

 albido, ad columellam rectam angulariter juncto. 



Axis ^ ; diam. ^ inch. Inhabits Loo Choo. 



Belongs to the group of which H. striatida is a type. 



Mr. A. E. Agassiz made the following communication 

 on the mechanism of the flight of lepidoptera : — 



The nervures of the wings of butterflies are so arranged as to 

 give the greatest lightness and strength ; they are hollow, with 

 their greatest diameter at the base of the wing, the point of great- 

 est strain, their diameter gradually diminishing to the edge of the 

 membrane. If a section be made across such a wing, parallel to 

 the axis of the body, we find very much the arrangement which 

 has been experimentally proved by Fairbairn and Stephenson as 

 giving the greatest strength of beams, as exemplified in the tubu- 

 lar bridge — in the insect nervure, as in the strongest beam, we 

 find the most possible material thrown into the flanges, and the 

 upright support as thin as practicable — in the insect wing we 

 have a very thin membrane connecting two flanges, whose section 

 is very great compai-ed to the membrane, with the additional 

 advantage that these flanges are hollow, increasing their strength 

 and diminishing their weight. In all Ave find the strongest ner- 

 vure placed either directly on or near the anterior edge of the 

 upper wing ; there is no such nervure in the lower wing, all being 

 of nearly the same size, as such a one would have prevented the 

 elasticity of the wing from assisting the flight to any considerable 

 extent. The lower wing is always partially covered by the 

 upper ; were this not the case, in the downward beat the resist- 

 ance of the air would cause the lower wing to become separated 



