LOPHOPUS, ALCYONELLA. 669 



three concentric series on the upper convex surface, the lower flat surface, on 

 which the colony moves along, being devoid of polyps. The statoblasts'are 

 provided with a double circle of long slender spines, ending in recurved hooks. 

 Alcyoiiella fungosa is a species commonly found in streams and ponds in the 

 form of brown clumps and nodules on floating timber, stems, sticks, etc. 



In the Pedicellinidie, which are mostly marine, the polypides are stalked, 

 the stalks arising from a creeping stolon ; the tentacles, which form an 

 almost complete circle round the mouth, are not capable of being retracted 

 into a sheath. In the aberrant genus, Ehahdopleura, the platform round the 

 mouth is drawn out into two long tentacle-bearing arms. In Gephalodiscus, 

 dredged up in the Straits of Magellan by the Challenger, the 

 oral platform is drawn out into twelve processes — six on each 

 side, armed with plumes of tentacles; the colony, which re- 

 sembles a branching, spiny, gelatinous sea-weed, is permeated 

 by canals along which the polypides can wander freely. In 

 most of the Lophopoda a lobe projects over the mouth; the 

 presence or absence of this character was made use of by 

 Allman for the purpose of classifying Bryozoa into two groups 

 — Phylactolfemata (guarded throat) and Gymnolsemata (un- 

 protected throat). 



The Bryozoa are found in the Palaeozoic rocks, and occur 

 in great abundance in the Chalk, the Cycloatomatous group 

 prevailing in the earlier formations. A classification is here 

 appended for reference : — 



Sub-class I. — Infundibulata — with a circle of tentacles, a, Chiloatoraata — 

 with a horny lid shutting down over the tentacle sheath (Flustra, 

 Bugula, Lepralia, etc.). b, Cyclostoniata — all calcareous; without a 

 horny lid ; without avicularia (Crisia, Tubulipora). c, Ctenostomata — 

 with a circle of bristles forming a kind of operculum ; never calcareous 

 (Amathia, Alcyonidium, etc.). 



Sub-class II. — Lophopoda — with horse-shoe shaped plume of tentacles or 

 arm-like processes bearing tentacles (Alcyonella, Pedicellina, etc.). 



[Note. — The name Polyzoa ia often used by English zoologists in place 

 of Bryozoa, but the latter term, definitely employed as a class name by 

 Bhrenberg in 1834, apparently has greater claima to acceptance. Biblio- 

 graphy — Johnston's "British Zoophytes;" Hincka' "British Marine 

 Polyzoa;" Allman's " Fresh-water Polyzoa ; " "Encyclopaedia Britannica," 

 Polyzoa (Lankester). 



