r*' 



13 



Rhynvhonclhi , sp. 



In the upper bed of iron ore one of the most freqnent shells is 

 a simply ribbed lihynchondlit , somewhat resembling Rh. velUcuta 

 of Hall, but too much distorted and too imperfectly preserved to 

 enable it to be determined with certainty. 



Dlsrina, sp. 



A small elevated smooth DiscuKi, marked only with very 

 delicate Hues of growth and near in form to the more elevated 

 varieties of Z>. oblongata, Portlock, from the Middle Silurian of 

 England. 



Mcginnhonbi onici'Ihitd, Hall. 



Perfect specimens of this beautiful little shell show that the 

 right valve is flatter than the left, and destitute of the cancel- 

 lated markings, having only concentric lines. When the valves 

 are closed the basal sulcus has very much the aspect of a byssal 

 aperture. These characters would a)ly this shell with Avicufuhr 

 rather than with ArcaiJa . 



Avicnld lamellosa, n. s 



Hinge line somewliat longer t'^an the breadth of the shell, and 

 about equal to its length. Left valve tumid, right valve less .so, 

 umbones apprcssed, base broadly rounded, anterior wing short, 

 but decidedly separated from the body of the shell, posterior 

 wing much larger. Surface smooth, but ornamented with concen- 

 tric thin raised lamella!, which are continuous over the wings 

 and body, and are elegantly waved, becoming distant from each 

 other on the lower side. Jjargest specimen 3 centim. long, 3*5 

 broad. At first sight this species resembles A. cquUatera of Hall, 

 but is quite distinct in form and markings. 



Aviaild, sp. 



A single left valve of a well-characterised species with the an- 

 terior wing neurly as broad as the posterior, and both flat and 

 smooth, or with microscopic concentric lines on the posterior one. 

 Body of the shell with about 15 radiating ribs, crossed by obscure 

 concentric ridges. I had at first regarded this shell as a variety 

 of -4. Honeijmani of Hall, but the anterior wing, when exposed, 

 showed it to be altogether different. I find it diflScult to dis- 

 tinguish the last-named species from A. ; • icerata of Hall, as 

 some specimens show radiating striae on the posterior wing, and 

 otherwise approach to that species. 



