656 MR. A. W. WATERS ON MEMBEANIPOEID^. 



in the Tertiary and Cretaceous periods, is represented by Chaperia 

 acanthina^ Q. & G., C. annulus, Manz., C. capensis, B., G. cristata, 

 B., O. cervicornis, B., ? C. cylindracea, B. ; and although. Jullien 

 took a character which only sometimes occurs, it has seemed 

 simplest to retain the name he gave. 



Xirkpatrick refers Glmperia acantliina, Q. & Gr., to Lepralia ', 

 but in Chaperia the avicularia have not a complete bar, whereas 

 in all the Lepr alias I have examined the bar is complete ; and the 

 muscular attachment of Lepralia is not quite similar. 



In what I should call typical opercula of Memhranipora, 

 namely, in the opercula of M. curvirostris, H., M. Flemingii, 

 Busk, Onycliocella angulosa, Reuss, there is on the distal edge a 

 well-developed flap (PI. 47. fig. 7) or bow; on the other hand, in 

 M. memhranacea, M. nitens, Hincks, there is only a thickened 

 border (PL 48. fig. 17). The structure of M. Mans, H., is 

 peculiar (PI. 48. fig. 16), and somewhat resembles that of M. La- 

 croixii (PI. 48. fig. 15) and M. calif or niensis, sp. nov. ; but with 

 these exceptions is unlike that of any other species, for the 

 operculum has a flap and is continued distally beyond this, 

 " forming a membranous extension which closes in the upper 

 part of the cell." 



Turning next to the ovicells, there are three groups, the 

 Memhraiiipora {Electra^ pilosa, the M. memhranacea, and the 

 M. catenularia groups, in which no ovicells are known in living 

 forms, whereas they occur in several fossils. M. pilosa is placed 

 by Busk, Hincks, and Norman in the genus Electra, and the 

 chief character upon which the separation is based is the absence 

 of ovicells. This is no doubt an important character, and the 

 form of the ovieell should always be duly considered ; but we 

 must be careful that we are not led too far and attach undue 

 importance to the ovieell until the mode of reproduction has 

 heen studied, remembering that sometimes the ovicells may be 

 of specific and sometimes of generic value ; whether we are ever 

 justified in going further than this cannot be decided at present. 

 In the genus Lepralia there are some species with, and some 

 without, external ovicells. Lepralia Pallasiana, Moll, is described 

 as without ovicells, nor in typical species from several localities 

 have I ever ibund any, but Mr. Hincks describes * one with 

 ovicells. Without having had an opportunity of examining it, I 

 Avsx unable to pronounce any opinion, but perhaps it should be 



* Ann. & Mag. Nat. Hist. ser. 5, vol. vi. p."77, pL s. fig. 3. 



