DuERDEN — On some neiv and rare Irish Polyzoa. 129 



korenii, has been the subject of an elaborate paper by Prof. Gr. 0. 

 Sarsinthe " Christiania Yidenskabs : Selsk., Forhandlinger, 1873." 



The characters of the family are thus given by Mr. Hincks : — 

 " ZocEcia horny, with an aperture and membranous area on the 

 ventral aspect ; borne on a rigid peduncle to which they are attached 

 by a movable joint, deciduous." 



The most important structural feature in the family is the presence 

 of an aperture or area, with a membranaceous covering, on the 

 ventral aspect of the cell, which is regarded as representative of the 

 aperture existing in many Cheilostomata. Through the genus Aetea 

 on the one hand, and Triticella and Cylindroecium on the other, Smitt 

 and G. 0. Sars have pointed out that the two great divisions of the 

 polyzoa, the Cheilostomata and Ctenostomata, are very closely linked 

 together. 



Genus. — Teiticella, Dalyell. 



Triticella, Dalyell (1848), Eemark. Animals. Scotl. ; G. 0. 

 Sars, Christiania Yidensk. Selsk. Forh., 1873, p. 397 ; Hincks, Brit. 

 Mar. Pol., p. 542 ; Farrella (part). Alder. 



Hincks thus defines this genus: — "Stem repent; zooecia with a 

 membraneous area on one side (the ventral), flat, or slightly 

 depressed ; more or less gibbous on the other (the dorsal) ; com- 

 pressed laterally, attached by a movable joint to a rigid peduncle. 

 Polypide without a gizzard." 



Prof. Sars, in his diagnosis of the genus loc. cit., p. 397, gives as 

 one of the characters that the " peduncles rise from a continuous 

 crust or a creeping stolon." He describes T. boechii as arising in 

 dense tufts fram a continuous crust, and T. horenii as being scattered 

 and rising from a delicate creeping stolon. Hincks follows him in 

 this, and also Alder in his description of T. pedicellata, which agrees 

 with that of T. korenii. 



In all these three species, which I have under examination, from 

 the west-coast of Ireland, there is a more or less continuous horny 

 crust, which appears alike in structure in the three forms when 

 removed from the crustacean on which the colony is growing. It 

 appears under the microscope as a very thin horny layer with circular 

 perforations, from which the peduncles arise. In specimens where 

 the individuals arise in dense tufts, as in T. horenii and hoechii, 

 the crust, with the perforations for the peduncles, is quite continuous ; 

 and the tissues of the animal under the crust can be traced as 



