CONCHIFERA. 



MARTESIA, Leech 



M. CLAUSA, n. s. 

 PL 22, Fig. 115. 



Shell elongate, cimeate ; beaks anterior, incurved, approach- 

 ing. Posterior cardinal margin sloping regularly towards the 

 extremity of the shell, which is narrow and rounded; basal 

 margin nearly straight. Anterior opening moderate in size, an- 

 gular, closed. Umbonal groove double, widening rather rapidly 

 below. Surface marked by regular lines, concentric on the pos- 

 terior part of the shell, and which, after crossing the umbonal 

 groove, run nearly parallel with the margin of the anterior 

 opening. 



Figure, slightly magnified. 



Localities: Pence's Ranch, Butte County; Texas Flat, Placer County; and 

 Tuscan Springs, Tehama County (Division A.). 



TURNUS, N. Gen. 



Shell thin, pholadiform; bearing internally a rib which rises 

 in the apex, and passes downwards and backwards to the basal 

 margin, in the same manner as, and posterior to, the umbonal 

 groove. Accessory plates unknown. Tube simple, thin. 



This genus appears to occupy a position in subfamily Teredi- 

 nina?, and to form, as it were, a link with the Pholadinse. With 



PAL. VOL. I. — 10 ( 145) 



