38 



spine, which as is known appeal's in very different degrees of development in a 

 number of members of this family. As a similar enclosure of the operculum is 

 also found in Menipea liausd Busk ', Men. Je/freysi Norman - and Scnipocellaria mar- 

 supiata Jull.^, it seems i)robable that the operculum in these species has a similar 

 structure. Besides in the species just mentioned, we find an independent opercular 

 valve in the Coilostegous genera Micrnpora and CeUiilarut, and in the genera of the 

 division Ascophora: Microporellu, IiuxTsiiila, Onchopora, Vrceoliporu, Clwrizopora, 

 Haplopoma, Adennellopsis and Tubncellarin. While we may briefly call such an 

 operculum as appears in most of the Malacostei/d an opercular valve, I would 

 propose the designation »simple o])erculum« for any opercular valve, which is 

 distinctly marked off from the frontal, membrane, and can consecjuently be isolated 

 as an independent formation. While the proximal edge of such an oi)erculum 

 forms as a rule a straight line it is more or less concave in a number of sj)ecies of 

 the genera Celliilaria and Tlutldinoporella, so that the hinge-line falls a little proxi- 

 mally to the edge, and in such cases the sim])le operculum does not fill the 

 whole zoa^cial aperture, the proximal part of which is filled by a membrane. 

 Within the division Ascophora the same thing appears in a new form from Singa- 

 pore belonging to the family Petraliiilae. Jul lien' has founded a genus: Clui- 

 perio, the species of which were formerly referred jiartly to Membrnnipora, and 

 partly to Monoporelhi, and Waters'' says regarding this genus: This group was 

 indicated by Jullien under the name of Chaperia, but while he based it upon 

 two lateral plates, which I have shown are for the attachment of the oj)ercular 

 muscles, and do not occur in all species, the important character is the form of 

 the operculum, which is separable, and which has at each side an elongate pro- 

 tuberance for the attachment of the muscles. « hi oi)j)Osition to Waters I would 

 maintain that the most important generic character is the two plates mentioned, 

 which I have found in all sjiecies I have examined, whereas the operculum 

 according to my investigations is subject to a fairly considerable variation. As 

 Waters refers both Meiiib. (j(ih-ala and Menib. crislata to Cli. <inniiliis Manz., we 

 must, before speaking about the operculum in the different forms, make the ad- 

 mission that our material is too small to venture on expressing an opinion as to the 

 identitj' of the two last-mentioned forms, which in any case are very closely con- 

 nected, hi a species, which under the name of Memb. cristata has been sent me 

 by Miss Jelly and which came from South Africa, the opercular valve occupies 

 nearly the whole of the distal half of the large oval aperture of the zooecium, 

 and is in its proximal portion furnished within each lateral rim with a very 



' 8, p. 20; '^, p. 44(i; » 43, p. 507; * 45, p. 61; ' 112, p. 655. 



