200 BULLETIN OF THE NATURAL HISTORY SOCIETY. 



This species is like Lingulella acutangulus Roem. of the Upper 

 Cambrian of Texas, but is larger and differs in the more acuminate 

 apex of the ventral valve, etc. 



Lingulella tumida, n. sp. PI. I., figs. 2a to c. 



A small round, thick-shelled species, of which only the ventral 

 valve is known. It resembles an Obolella in form, but has a corneous 

 test, and a pedicle groove. 



Sculpture. — The surface of the shell is marked by rounded con- 

 centric ridges, some of which show a beaded crest. 



Size. — Length 6 mm., width 5 mm. 



Lingulella Martinensis, of the Protolenus Zone, is something like 

 this in form, but is much larger. Lingulella Ella, H. k W., of the 

 Middle Cambrian of the West, is like this in size and outline, but the 

 surface markings are finer. 



We now come to two species whose reference to the genus Lingu- 

 lella is doubtful, because we have not recognized the pedicle groove, 

 and because especially as regards the second, the form, etc., is sug- 

 gestive of Lingula rather than Lingulella. 



Leptobolus ( 1 ) collicia, n sp. PI. I., figs. 3a to e. 



A small oval species somewhat pointed in front. Margins flat- 

 tened, especially in the posterior half. Remarkable for the peculiar 

 spoutlike flexure at the front of the dorsal valve, acquired in the 

 later stages of growth. A corresponding pair of grooves appears in 

 the anterior part of the ventral valve. This peculiarity of form simu. 

 lates the sinus of the articulate Brachiopoda. 



Sculpture. — This consists of fine concentric ridges, visible only with 

 the aid of a lens. These sometimes anastomose. 

 'Size.- Length 10 mm., width 6 mm. 



Leptobolus atavus, n. sp. PI. II., figs. \a to/ 



Shell calcareo-corneous. Ventral valve somewhat pointed behind. 

 Hinge area very small and obscure, not more than a tenth of the 

 length of the valve. Margins of the valves arched downward all 

 around, except at the apex of the ventral valve. The median depres- 

 sion of the dorsal valve indicates that the central group of muscles 

 are set far forward in that valve, as they are also in the ventral valve. 







