400 



THE YOUNG NATURALIST. 



anterior side short and rounded, the posterior j 

 long and rather angular ; the valves are ridged j 

 concentrically , the umboes covered with wavy | 

 protuberances : the color is olive-green with : 

 rays of brighter green, interior pearly. They 

 inhabit rivers, streams and canals, and are 

 found mostly in the south and east of the 

 country. 



Pictorum. — This shell is longer than the ; 

 last, the anterior side is rather short and 

 rounded, the posterior side long and rather 

 angular ; the valves are ridged, shewing 

 stages of growth, the color is olive-brown, the 

 interior pearly. They may be found in 

 similar situations to the last, and in the same 

 parts of the country. 



Margaritifer.— This shell is long and 

 rather arched, both ends are rounded, the 

 anterior very short, the posterior long, the 

 valves ridged concentrically and covered with ; 

 a black epidermis. These are pearl bearing 

 molluscs, they dwell in mountain streams, and 

 rapid flowing rivers throughout the country. 



FAMILY, CARDIACEA. 

 Genus, Pisidium. 



These fresh -water Cockles are mostly of j 

 very small size, the shell horny with the two 

 valves equal ; the anterior side is longer than the j 

 posterior, the hinge is toothed. The animal 

 has the siphons united. The following are the 

 names of the species, Amnicum, Obtusale, \ 

 PustUum, Nitidum, Casertanum, Pulchellum, and I 

 Henslmvianum. 



Amnicum. — The largest of the genus, 

 being fully a third of an inch m length, the 

 posterior side is short and rounded, the anterior 

 is long and rather angular ; the valves are 

 very distinctly striated in the direction of the 

 lines of growth, in color greyish-olive. It may 

 be found in all parts of the country, in streams, 

 &c, generally buried in the- mud. 



Obtusale-— A small shell about a sixth of 

 an inch in length, nearly circular, and with 

 rounded striated valves, the umboes swollen, 

 and they are almost central, both anterior and \ 

 posterior sides are rounded. It is found in 



slow streams, &c. 



Pusillum — This is about the same size as 

 the last, but is not so round a shell, the anterior 

 side is rather oblique though rounded, the 

 posterior is also rounded but shorter ; the 

 umboes are uot so swollen as in Obtusale, though 

 slightly so. It may be found throughout the 

 country, in ponds, &c. 



Nitidum. — This. shell israther larger than 

 the last described, the umboes are nearly cen- 

 tral, the anterior side rather oblique, both 

 sides rounded, it is striated and rather glossy. 

 It is found in ditches and stagnant water. 



Casertanum —This shell is about the 

 same size as the last, the anterior side rather 

 long and oblique, the posterior side short and 

 rounded; it is greyish and dull. Itmaybemet 

 with in all parts of the country, in streamsand 

 ponds. 



Pulchellum.— This is very minute, being 

 the smallest of the genus ; the anterior side is 

 the longer and is rather oblique, both sides 

 are rounded. It may be found in stagnant 

 water, ditches, &c, throughout the country. 



Hcnslowianum — This is a rather larger 

 shell than Pusillum, the anterior side is rather 

 long and angular, the posterior short and 

 rounded ; it is rather yellowish and glossy, and 

 is finely striated. It inhabits ponds and ditches, 

 but is not so generally distributed as the other 

 species. 



Genus. Cyclas. 

 In this genus the shells are larger than in 

 Pisidium, of similar shape and with toothed 

 hinge, but with the posterior side of the valves 

 the longer. The animal may be distinguished 

 by the siphonal tubes being only partially 

 united, they are united for a portion of their 

 length, and are then divided. The species 

 are Rivicola, Cornea, Pisidioides, Ovalis and 

 Lac u sty is. 



Rivicola- — This is the largest of the genus, 

 the shell measuring above three quarters of an 

 inch in length, it is oval and thin, both sides 

 are rounded, the anterior being slightly the 

 shorter, it is bluish-white inside and olive-green 

 outside, glossy and striated ; the umboes are 



