10 



Escliarina spiiiifera, the two laii^e distal projections which a[)peai- in a number 

 of species of the genus Thalamoporella (PI. Via, ligs. 4 a, 5 a) and llie two corre- 

 sponding projections in the genus Claviporella (Pi. XX, fig. 10 a). Undoubtedly also, 

 the very long and thin spines which appear at the edge of the calcified, arched fronlal 

 wall of ^Lepralici< Poissoni in a very unusual way, belong to this division, and also 

 the likewise long and thin spines which somewhat scattered and in great numbers 

 surround the anter of the ajierture in Scliizofxirclla hiscridlis Hiucks ', and 

 which give the impression of having been formed lound a number of the nume- 

 rous scattered pores which appear in this species, in the same way as the very 

 short arched projections which occasionalh' appear round ocrcial pores, for in- 

 stance, in the species of the genus VJaviporelln. The hue acrojielal spines like the 

 marginal ones are always formed by a Gymnocyst, but in PordUt (?) corniita (PI. 

 XVIII, fig. () a) the endoooecium in a numJ)er of zoa^cia is furnished with one or 

 more hollow spine-like processes which in the same manner as the acropetal 

 spines have a ring-like origin and are no doubt formed by chalk-particles depos- 

 ited under the membranous ectooa>cium. These projections, however, are in no 

 inner connection with the ooecium and cannot therefore be looked ujion as true 

 spines. 



3) The bildininale spines, which have hitherto only been found in the family 

 Catenariidce and will be more fully spoken of under this family, spring from the 

 free margin of a moie or less developed sinus (Ihc sternal sinus), from the margin 

 of which also an inner Cryptocyst lamina takes its origin. As these spines issue 

 from a margin in which a Gymnocysl and a C-ryjitocyst meel, they must of 

 course be two-layered, their outer layer l)eing formed by the Gymnocyst and the 

 inner by the Cryptocyst. They attain their highest development in the genus 

 Costicella (PI. XII, figs. 1 a— 1 d, PI. XX, figs. 8 a— 8 b, fig. 9 a). 



The morphology of the zooecium. 



As is known we can in the cheilostomatous Bryozoa distinguish between six, 

 as a rule well-separated, walls, namely, the two lateral, the two terminal, the 

 basal and the frontal. It is generally difficult however to distinguish exnclly 

 between the lateral walls and the fionlal wall (or basal wall) in species which 

 appear in single rows, and in those zoci'cia which arise by superficial gemmation 

 and in most cases in moie or less erect {josilioii (I'or instance in the ('.cltcpord 

 and Iloloporclld s])ecies) only llie basal wall is sliar|)ly hounded, the other walls 



' 3U, p. 250. 



