315 



the covering membrane in many forms is extremely thin and very readily torn, 

 and the absence of il in one or two colonies is no sure evidence, that it is 

 lacking in the species examined. Secondly I have become somewhat doubtfull as 

 to the systematic significance of this character, as in the genus Microporella some 

 species, for instance M. ciliala, possess a covering membrane while it seems to be 

 lacking in others. Thus I have not been able to find it in a fresh colony from 

 Norway in which the young zooecia in the growing margin show the membranous 

 frontal wall well-preserved, and the same is the case with a nearly related species 

 from Japan, appearing in two-layered, /''/(/.s/m-like, richly branched tufts. 



Escharella' Gray, char, emend. 

 Mucronella Hincks |). \^. 

 Lepralia Hincks p. p. 



The zod'cia, which usually have 2 — 8 spines, are provided with a well-devel- 

 ojjed, .sometimes even strongly developed vestibular arch and usually with a more 

 or less developed often mucronale peristome, which rarely embraces the distal 

 margin of the aperture. The operculum is mostly thin, almost membranous, some- 

 times more or less strongly chitinized and in the first case the proximal margin 

 of the aperture is generally protected by a median tooth. No (wicalaria. The 

 oaria, which in some species are endozorecial and covered by kcnozoa?cia, have 

 no pores. Marginal [)ores appear as a rule, rarely scattered pores. In the distal 

 half of the zoa'cium there are numerous small (12—18), uniporous, contiguous 

 pore-chambers, which have arisen by division of three elongated, multiporous 

 chambers (a distal and two lateral). 



To this genus belong the following species: E. iinmersa, Flem. (^ Miicroiiclld 

 Peachii, Johnst. + '^^- ventricosa, Ha.ssall), E. (Miic) variolosa, Johnst., E. abiissi- 

 cola, Norman (= E. laqiieata, Norm.), E. (Mm:) microstoma, Norman, E. emmro- 

 mita, Smitt-, E.stemisloma, Smitt-, E. (Mm:) spimisissima^, Hincks, E. (Lepralia) polila, 

 Norman, E. (Lepralia) multispimita, Busk^ and E. (Mm:) dia})liami, Mac Gillivr. 



The vestibular arch, which in this genus varies greatly in form and extent, 

 reaches its greatest development in E. diaphana and E. microstoma, in which two 

 species it reaches far into the zoa-cium in the form of a pent-roof. A median 

 tooth is lacking in E. microstoma and E. polita, and the two last possess a strongly 

 chitinized operculum with a convex, proximal margin. The oa'cia are surrounded 

 by kenozooecia in li. diaphana, E. (dnjssicola, E. polita and also, so far as I can 

 determine on a small colony with a single, broken ooccium, in E. microstoma. 



' 84, p. 116. ^ 101, p. 1129—30. ' 28, p. 53. ' 8, p. 160. 



