152 Rev. T. Hincks's Critical Notes 



As yet, however, this section of Busk's Adeonella has not 

 been studied with sufficient thoroughness to admit of an 

 accurate definition. Amongst the species which Waters 

 refers to it one at least is an alien, A. lyolystomella, Reuss 

 {Pallasii, Heller), which is, as I have already pointed out*, 

 an undoubted Sckizoporella. This species, which is furnislied 

 with a median sinus, is destitute of avicularian cells, and it 

 is doubtful whether the cells lining the margin of the zoarium, 

 whicli are somewhat larger than the other zooecia, but exhibit 

 no further peculiarity, have a claim to be accounted ooecial, or, 

 as I propose to term the cells modified for reproductive pur- 

 poses, gonoecia. The so-called pore is a gap in the extension 

 of the peristome above the primary orifice, which is bridged 

 over above by a calcareous bar uniting the two lateral avicu- 

 liferous prominences, and completing the secondary orifice. 

 A similar form of peristoraial opening occurs also in Gephy- 

 royliora polymoT'plia^ Busk, and in other species. It has no 

 special connexion with the family of the Adeonidre. 



The figures in the ' Challenger ' lieport show that there 

 are several forms amongst the so-called Adeoiiellce in which 

 the orifice is distinctly sinuated ; and it is stated that the 

 commonest way in which the pore is formed is " by the 

 constriction off" of the lower part of the orifice, which in such 

 cases is more or less deeply emarginate or sinuated " t- In 

 the account of Adeonella regularis, Busk, which is furnished 

 with a "bridge" and with tlie equivalent of a peristomial 

 opening, we are told that " a very minute suboral pore is 

 occasionally formed by the cutting away of a portion of the 

 labial fissure " |. 



The account leaves us in doubt whether this is more than 

 an accidental thing. If the pore is not an essential part of 

 the structure, I should be inclined to refer A, regularis to 

 Schizoporella. So far I have examined no species in which 

 the formation of the pore could be traced to a constriction of 

 the sinus. 



Waters [loc. cit.) has drawn attention to the occurrence of 

 an oral sinus in some of the Adeonellce, and emphasizes the 

 importance of this character ; but amongst the species which 

 he has gathered into his restricted genus Adeonella, two {A. 

 intricaria and A. pectinata) are described as having the lower 

 margin of the orifice straight and entire. The mere presence 

 of a peristomial opening can hardly be made the basis of a 



* "ThePolyzoa of the Adriatic,'' Ann. & Mag. Nat. Hist, for March 

 1886, p. 268, pi. X. fig. 7. 



t ' Challenger ' Report, 1884, p. 178. 

 t Ibid. p. 187. 



