OF THE FAMILY BACILLARIA. 153 



ECHINELLEA. 



The section Echinellea contains those Bacillaria which are 

 /7,rcr/, that is, attached either by their extremities, or by a pedicel, 

 to other bodies. They are all siliceous. 



The section Lacernata includes those which have a double 

 covering. They consist of groups of siliceous individuals, sur- 

 rounded by a common gelatinous mass, or enveloped by a 

 membranous tube. 



As many species of each of these sections are often found 

 spontaneously or accidentally separated from their pedicels or 

 tubes, there is great chance of mistaking them for species of 

 Naviculacea. 



Fixed by one end, carapace or lorica siliceous, simple, broader 

 than long, catenate by imperfect spontaneous division, individuals 

 making various angles loith each other, and connected by a narrow 

 isthmus or neck-like process. 



Two species of this genus have been detected, namely, 

 I. enervis, and I. obliquata. Neither of these have, to my knowl- 

 edge, yet been detected in the U. States ; but as the latter is a 

 pelagic species, wiiich has been found in places so different and 

 distant from each other as Iceland, England, the Canary Islands, 

 Cape of Good Hope, &c., there can be little doubt that it will yet 

 be found gi-owing on some of our marine Algae. The first 

 specimen which I ever saw, I detected on a dry specimen of 

 Odonthalia dentata from Iceland. I have since received fine 

 English specimens from E. J. Quekett, Esq. of London. Few 

 microscopic objects exceed in beauty these little gems of the 

 ocean. I have proved that their carapace is siliceous by the 

 proper chemical tests. A good idea of the general form of tliis 

 genus may be got from Plate 4, fig. 153, of Pritchard's Infusoria. 

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