On the Determination of Br yozoa. By A. W. Waters. Ill 



below the oral aperture, and having the proximal edge of the 

 aperture straight; while other species have a pore which is 

 peristomial and the aperture has a broad sinus, that is to say, the 

 two most important characters are different, and I think atten- 

 tion having been called to this, that it will be seen that they must 

 be kept distinct. 



Mr. Busk, however, points out that " in the entire group " 

 (speaking of the family Adeoneae) " the avicularian mandibles, both 

 large and small, always exhibit a projecting point or articular 

 process at each end of the base." This is certainly a curious fact, 

 but in order to see what value must be attached to it we must 

 examine whether it is only in this group that this process obtains, 

 and when we have found it in various genera it is only reasonable 

 to conclude that we must not attach generic importance to this 

 when other characters are widely divergent. In Cribrilina radiata 

 (fig. 34) this process is pronounced, and it is also seen in the 

 mandibles of Fhistra armata (fig. 2) and F. foliacea (fig. 3), and 

 the structure of several Memhraniform where the basal portion is 

 thicker in the centre than at the corners, is only a modi- 

 fication of the more distinct process of the Adeonese. This is 

 shown in M. curvirostris (fig. 40) and M. Flemingii (fig. 43), 

 and occurs very distinctly in mandibles of a Memhraniioora allied 

 to M. dentata d'Orb.* 



These processes in the mandibles of Cellepora and Adeona lead 

 us to the consideration of the importance of such modifications. 

 They indicate difierences in the muscular attachments, and both 

 here and in the opercula it is really the muscular system which 

 has the greatest classificatory value ; but this is best studied by 

 means of the variations in the chitinous parts. This Mr. Busk 

 does not seem to have fully appreciated ; for the muscular attach- 

 ments or projections for the purpose are not figured by him, where 

 preparations in my possession show such characters very clearly. 

 The pattern of the mandibles, if we may thus call it, depends upon 

 there being either two chitinous layers in places, or upon a thicken- 

 ing of the chitin. In some cases this may be directly for the at- 

 tachment of the muscles, but more frequently it seems to be rather 

 a thickening to give support to the point of muscular attachment. 

 There are a few cases of very thin mandibles, some of which may 

 be stained, instead of showing up yellow against the coloured tissue. 

 As examples, see the mandibles of Mucronella coccinea (lig. 25), 

 Schizoporella arrogata (fig. 26), and the large mandible of lietejpora 

 Coitchii. 



* Under Adeondla I bIiouM ini'ludo A. polijmorpha 15., A. plutidca 15., A. 

 intrkarui B., A. alltintka B., A. pcrAinata J J. (?), A. polystomctta Hhh. (^Es(liai-<t 

 Palhmi Hi;ll) ; but Mkrojiorella disloma li., M. cdscinaporn Itaa., M. lichenoides M. 

 Ivl., and M. fism IliiiclcH, I wliduld not place in tliiy goniiH. 



