Bacillaria.] THE INFUSORIA. 223 



300. MEBIDION vwnale (Enchinella, Greville). The 

 spring Meridian has a striated wedged-sbaped lorica, 

 truncated and dentated at the anterior extremity. Fig. 177 

 is a spiral cluster; these sometimes appear circular. Fig.tfS 

 is a cluster separating, in which some are seen from the 

 side. Length of single specimen, or wand, 1-1 150th to 

 l-240th. 



301. MEBIDION? panduriforme (Exilaria, Berlin Trans.) 

 The fiddle-like Meridian has a sinuous, wedge-shaped 

 lorica, of the form of a violin. Length 1 -430th. 



SECTION III. Attached. ECHINELLEA. 



Genus LXV. ISTHMIA. The Infusoria belonging to 

 this genus are attached by one of their extremities to 

 sea- weed, &c. ; they are developed in the form of a chain, 

 have a simple siliceous lorica, broader than it is long, 

 articulated to each other by a short neck-like process 

 hence their name, Isthmia : this part is sometimes called 

 the foot, and near which a single opening in the lorica 

 is observable; the lorica is not destroyed by heat or 

 acids. In the interior is a floccose substance, analogous 

 to ova. Self-division ensues along the short axis of the 

 body : hence it is properly longitudinal, though it appears 

 transverse. 



302. ISTHMIA obliquata (Diatoma obliquetum, Lyngbye). 

 The ribbed Isthmia is nearly square, with cellular, middle, 

 and transverse striated ends. Found in sea Algae. Size 

 of single animalcule l-90th. 



303. ISTHMIA enervis. The smooth Isthmia resembles 



