MR. A. W. WATERS ON MEMBRANIPORID^. 675 



The first clear description of this common and widely dis- 

 tributed species was given by d'Orbigny in 1842 (the date on tbe 

 part of the volume), but Busk in his paper considered this was 

 the tuherculata of Bosc. Bosc gave no figure, and the descrip- 

 tion, which is most meagre, seems more probably to refer to 

 M. pilosa. His giving the locality European Seas makes this 

 probable, though it is quite pos5*ible that he confounded more 

 than one species. Flustra dentata, Miiller, which he gave as a 

 synonym, has been considered to be a variety of pilosa. Although 

 this form is so common, it has never been thoroughly described, 

 nor have I had the opportunity of examining any spirit-specimens. 



Mr. Kirkpatrick called my attention to two comb-like pro- 

 cesses (PI. 48. fig. 7) in the interior of a specimen from Angola, 

 which I at once perceived must be compared with the single 

 comb-like process in M. nitens (PI. 48. fig. 5) ; but although they 

 may be spoken of as generally occurring in the specimens from 

 this locality, it does not seem to be a character upon which a 

 new species can be founded, as it exists in M. tehuelcTia from 

 other localities, though often in an aborted form. 



The stalks supporting these combs arise from the lower part 

 of the front calcareous wall very near the distal border. It is 

 directed downwards, spreads out laterally, and carries a number 

 of fine pointed teeth (5-12). In specim.ens from Angola and 

 San Pedro, these combs are found generally, and there are 

 usually a pair, though one only occurs in some zooecia, especially 

 in those from which two * zooecia grow, also occasionally there 

 may be three combs. The zooecia are almost divided into two 

 parts by these stalked combs. In the Kurrachee specimens 

 there are aborted stalks in the same position, but the serrate 

 structure is wanting, while in the specimen from California I do 

 not find either stalk or comb. 



The position of the combs in M. tuherculata and M. nitens is 

 much the same as that of the denticle in M. Mans and Jf. Savartii. 

 Until living specimens are examined, the function may remain 

 obscure, and from the position in the posterior part of the 

 zooecium it hardly seems probable that it is the protection of 

 the ova. 



There are also numerous small cervicorn spines or rays pro- 

 jecting inwards from the walls near the base. These remind ua 



* In other species where there are a pair of tubercles or avicularia, the same 

 economy is frequently exhibited. 



