14 Observations on the Terrestrial 



Periostraca slightly wrinkled by lines of accretion ; numerous 

 short rugre also run obliquely across the incremental lines. {Plate 

 2, Fig. 9.) 



Buccal plate, (Fig. 26,J) crescentic, pro- 

 duced in the middle of cutting edge, form- 

 ing a large rounded beak, on each side of 

 which are two smaller projections. 



Lingual membrane 60-23-1-23, central 

 plate nearly square, tridentate, central den- 

 ticle long, slender ; laterals three, (Fig. 27, 

 > Fig. 26. a.,) outer posterior portion somewhat point- 



ed, bidentate, larger denticle occupying nearly the centre of plate, smaller 

 denticle close to the outer edge of plate. Third lateral irregular in shape and 

 smaller than first and second laterals. Uncini having long claw-shaped denti- 

 cles, anterior portions abruptly bent inward. (PI. 6, Fig. 21.) 



This species is nearest allied to H. electrina ; it differs from that 

 species in the following particulars : it is nearly one third smaller 

 than H. electrina, its color is quite different being nearly white 

 with a greenish tinge. The buccal plate is much longer and has 

 a posterior expansion which we do not observe in H, electrina ; 

 the lateral terminations of buccal plate are somewhat rounded, 

 while in H. electrina the same portions are pointed. By comparing 

 the figures of the dentition of the two species several important 

 differences will be noticed; the lateral plates are broader and 

 shorter than in H. electrina, the uncini are abruptly bent inward 

 at their anterior portions and the number of plates stands thus : 

 60-23-1-23, so that we have a less number of plates in a row, but 

 a greater number of rows than we obtain in H. electrina. It 

 might often be mistaken for the young of H. indentata which it 

 resembles very much in form and color. Has been met with in 

 several portions of the southern parts of the State. The umbili- 

 cated variety of H. indentata may prove to be this species. "We 

 take the liberty of naming this species after W. G. Binney, Esq. 



Hyallna arborea, Say. 



Found everywhere in abundance. 



The incremental stria on the shell are barely visible, there are 

 also minute close-set revolving lines. The whole surface of the 

 shell appears to be marked Avith minute dots which do not 



