426 Rev. M. J. Berkeley on Ditrupa and Filograna. 



animal of which indeed I have seen only a single specimen ; but this was 

 enough to prove it most clearly congeneric with Dentalium subulatum, 

 though from the complete evaporation of the spirit in which it was pre- 

 served and the circumstance of the surface of the operculum being over- 

 grown wiih Ceramium repens and another minute Akjce, I was not able 

 to understand its structure sufficiently to give a figure. I at first thought 

 that there were some appendages to the operculum: nor from the 

 extreme minuteness could I ascertain so certainly the nature of a third 

 substance, in addition to the two .^/(/<e above mentioned, as to pronounce 

 decidedly upon the point with such scanty materials. It is highly pro- 

 bable that the other minute British Dentalia will prove to possess an 

 animal of like structure, though possibly even in that case it would be 

 requisite to place them in a distinct genus. 

 The characters of the genus 



Ditrupa 



are as follows. 



Shell free, tubular, open at both ends. 



Operculum fixed to a conical pedicellated cartilaginous body, thin, 

 testaceous, concentrically striate. 



. BranchicB 22 in two sets, not rolled up spirally, flat, broadest at the 

 base, feathered with a single row of ciHa. 



Man</e rounded behind, slightly crisped, denticulated in front, strongly 

 puckered on either side. 



Fascicles of bristles 6 on each side. 



I take this opportunity of referring to the two SerpulcE described in 

 Vol. 3, p. 229. Since the account there given was published I have 

 dredged several specimens of Serpulu Aninclo*, and find my former 

 observations confirmed. It belongs to the ti;enus Sabella as characterised 



* Serpula Arundo, Turton, Serp. tubiilaria, Moi.t, The latter name being 

 the original ought to be retained, and the species named Sabella tubularia, 

 Serpula tubularia, Turt. is quite a different species, and the same with Ser^. 

 vermicularis, Lam., excluding var. b. I am obliged to Dr. Johnston for calling 

 my attention to this point in Loudon's Magazine of Natural History, vol. 7, 

 p. 126. 



