of its upper latus, smallness and shape of its infra-median latus, form «>t the carinal latus etc.) 

 the present species is. however, so different, tli.it it can \«- distinguished from the above-named 

 spe. ies at first sight. 



alpellum praeceps n. sp. PI. \ 111, fig. i ;,. 



Valves fourteen, i by .1 velvety membrane; margins of valves nol everywhere to 



distinguished. Carina with the umbo at the apex, simply and strongly bowed, with a flat 

 roof bordered by ridges \ chitinous interspace between the carina and the other valves. 

 Rostrum covered by membrane, narrow, elongate. Infra-median latus small, triangular. Carinal 

 latus with the umbo nol far from the base, al the tip of an obtuse angle formed by the longer 

 upper and shorter under half of the carinal margin. 



This species is represented by one specimen only. 



The capitulum is covered l>y a chitinous membrane which has a villous or velvety 

 appearance. Thé little hairs are especially conspicuous along the tree margin of the carina. As 

 shown in the figure the margins of the valves in consequence of the presence of this covering 

 can not everywhere be made out distinctly. The carina is separated from the Other valves by 

 a chitinous interspace which is broadest between the tergum and the carina. The capitulum is 

 rather steep [praeceps] and elongate, being twice as long or high as broad. The occludent 

 margin is slightly, the carinal margin strongly convex. The apex of the tergum and of the 

 whole capitulum is in consequence pointed and very slightly recurved. 



The se ut urn has tin- ordinary shape ; the occludent margin is convex in its upper part. 

 The apex forms a very distinct recurved projection over the scutal margin of the tergum. The 

 scutum is about twice as long as broad. 



The tergum is triangular. Its occludent margin is convex; its carinal margin nearly 

 straight. Where these two margins meet the pointed and feebly recurved apex is formed. 



The carina is simply and rather strongly bowed with the umbo at the apex. Its roof 

 increases in width from the apex downwards, longitudinally hollowed out, being bordered by rather 

 prominent ridges. The sides of the carina have about the same width over the whole length. 



The upper latus is trapeziform: the carinal margin runs parallel with the scutal one. 

 The umbo is at the apex, which is very slightly produced. 



The rostrum is very narrow, covered by membrane, overlapped at each side l>y the 

 lateral margins of the rostral latera. 



The rostral latus is quadrilateral, with the scutal or upper margin uplifted and 

 forming the continuation of the upper margin of the carinal latus. The length of the upper 

 margin is less than twice the length of the basal margin of the same valve. 



The infra-median latus is very small, triangular, with the umbo at the apex. 



The carinal latus is rather large and irregularly quadrilateral in shape. The upper 



part of the carinal margin is slightly hollowed out, the under part slopes into the basal margin 



and is convex. Where the two parts of the carinal margin meet the umbo is formed, which 



very slightly projects beyond the line of the carina. The lateral and upper margins meet at a 



blunt angle. The basal margin can hardly l>e distinguished as a special margin. 



114 



