Polyzoa of the Adriatic. 261 



but he may possibly have only examined cells furnished with 

 the ovicell (in his figure every cell bears one), and in this 

 case two of the spines would probably be covered. Looking 

 to the general resemblance of the two forms, I have no hesita- 

 tion in identifying them. 



On some of the specimens from the Adriatic the primary 

 cell is present (PI. IX. fig. 3). The shoot commences 

 with a simple stem of some length, which gradually widens 

 upwards from the very slender base, and terminates above in 

 a single cell. This cell is rudimentary, having an aperture 

 which is very short as compared with that of the ordinary 

 zooecia, and surrounded by a number of tall spines, which 

 originate outside the margin. The pair of opposed spines is 

 also present on each side at the top. At tlie back of the 

 primary cell two other zooecia are developed which diverge 

 and give origin to two branches. There is a slight peculi- 

 arity in these cells j an additional spine is present on the 

 margin of the aperture between the bottom of it and the avicu- 

 larium, but in all other respects they are normal. The 

 specimens which I have seen are detached, so that nothing can 

 be known of their habitat. Mr. Busk's are all on the shells 

 of Ditrupa. 



Range. Madeira. 



Bugula gracilis^ Busk. 



Characteristic specimens occur on seaweed, but showing 

 no trace of the curious appendages with which the variety 

 uncinataj mihi, is furnished *. At the same time a careful 

 examination of them leaves little doubt on my rnind of the 

 specific identity of Bugula gracilis and the form uncinata. 



liange. Madeira (form uncinata) ; Britain ; North America. 



Bugula plumosa ^ Pallas, form aperta. n, 

 (PI. IX. fig. 6.) 



Zoarium somewhat rigid in habit, branches rather long, 

 fan-shaped, divided and su])divided dichotomously, disposed 

 subspirally round the stem. Zooecia biserial, alternate, elongate, 

 narrowing slightly downward; aperture occupying fully three 

 fourths of the front, rounded below, the outer margin more or 

 less bent inward, carried out above into a strong subconical 

 spine, and bearing a small avicularium, which is placed a 

 short distance from the top. Ooccium extremely shallow, 



* * British Marine Polyzoa,' vol. i. p. 86, 



