246 Rev. T. Hincks's Contributions towards a 



This is a smaller species than the last, and the cells are 

 more closely packed together than in D. elongata, and less 

 erect. There is a great difference in the spinous armature of 

 the two forms, and their avicularia are unlike. At the same 

 time the two species are closely allied. 



Diachoris costata, Busk. (PI. IX. fig. 4.) 



I have received specimens of this species from the Falk- 

 land Islands (the station at which it was obtained by the 

 ' Challenger ' expedition) ; growing on one of the red weeds. 

 They exhibit a peculiarity which is not noticed by Busk. 

 Gigantic avicularia are present here and there on the mar- 

 ginal or outside cells, two or three times as large as 

 those which are borne on the inner cells. This is common 

 amongst the Bugulce, to which Diachoris is most closely 

 allied. These avicularia are short and very thick, and of 

 equal width throughout ; the beak is not prominent, rising 

 very little above the top of the subjacent chamber (PI. IX. 

 fig. 4 a). There seems to be a certain definiteness in the mode 

 of growth in this form (as in other species of Diachoris), 

 which, indeed, we might expect. 



Diachoris Maydlanica, Busk. (PI. VIII. fig. 2 a—d.) 



Busk describes the mouth of this species as circular, with a 

 thickened, annular peristome*. As Waters has already 

 pointed out, this is an error f ; the orifice is arched above 

 and straight below. But when the operculum, which has ;i 

 thickened edge on the inner side, is thrown open, it presents 

 exactly the appearance described by Busk (PI. VIII. fig. 2 c), 

 and probably this may be the explanation of the mistake. 



The avicularium of this species is very remarkable ; it is 

 of great length, slender, and with very graceful outline. The 

 anterior portion is carried out into a long neck-like extension, 

 slightly bent at the extremity. The mandible is long, with a 

 triangular base and attenuated above. The area behind the 

 mandible is very large. 



The genus Diachoris, as originally defined by Busk, must 

 be regarded as a purely artificial division. But most of the 

 forms which have been ranked under the name present well- 

 marked characters, of much significance, and are properly 

 associated as a natural group. They have the cell of Bugula 

 and are furnished with the capitate and articulated avicularium 

 so characteristic of that genus. Indeed it is very questionable 



* Brit. Mus. Catalogue, parti, p. 54 ; 'Challenger' Polyzoa, part i. 

 p. .",-.i. 

 f " Bryozoa of the Bay o( Naples," 'Annals' for Feb. 1879, p. 121. 



