THE NAUTILUS. 
99 
and, as a rule, are covered with a black or brown coat, sometimes 
so thick that they appear to be globules of dirt, and only a sharp 
eye may recognize them from the hair-like free line along the edge. 
Some old specimens are badly eroded. 
Pisidium punctatum, n. sp. Figs. 7-12. 
Shell minute, iuequipartite, high, oblique, strongly ventricose, 
almost globular, regularly and sharply striated, microscopically 
rugulose, whitish; anterior part moderately long, the edge above 
oblique, almost straight, end slightly angled, rather inferior ; anterior 
part short, truncate, slightly angular above, rounded below; superior 
and inferior margins moderately curved, the former rather short, 
the latter long ; scutum little, scutellum moderately marked, both 
forming slight angles; vertical section heart-shaped, horizontal, 
short, lanceolate-rhombic; margins very slightly acute; beaks 
moderately full and prominent, with a longitudinal, slightly oblique 
ridge (sometimes obsolete) below the culmination ; nave moderately 
thick, whitish, with crowded, small pits, from which it appears as if 
dotted; hinge moderately strong; cardinal teeth fine, in the left 
valve two, lamellar, longitudinal, about equally long, a little curved, 
almost parallel, the upper little anterior; in the right valve one, 
longitudinal, little curved, lamellar, the posterior end slightly thick¬ 
ened ; lateral teeth rather small and thin, in the left valve one, 
pointed, in the right valve two, the outer quite small; hinge-list fine, 
rather regularly formed ; ligament rather long and fine. 
Size; long 1*8, alt. 1*6, diam. P3 mill. 
Soft parts colorless, rest whitish. 
Habitat: Ohio; Tuscarawas River, Bear Run, tributary to the 
Mahoning River, Portage Co., a spring brook at Rootstown Station, 
Portage Co., emptying into tbe Cuyahoga River (Lake Erie and 
St. Lawrence drainage) ; in all places collected by the writer. 
Figures 7-9 represent an adult, 10 a young specimen, scale 
15X1 ; fig- 11 the hinge, 11a the dorsal aspect of the cardinal teeth 
in the left valve; fig. 12 shows a remarkable abnormity of the car¬ 
dinal tooth in the right valve. 
This species resembles somewhat Pis. compression Prime, in hav¬ 
ing a ridge or appendage, but not in the seme place, as it stands on 
the outside, below the culmination of the beaks, while in the mature 
P. compression it has its place rather on top. The shape of the 
shell is different, and the size is very much smaller, its bulk being 
only about one-tenth of that shell. And while the upper part of 
