217 



sidered a separate, though very closely allied species, hi the genus Catenaria it 

 seems to be constant. 



We have already observed (pag. 215), that a more or less complete coales- 

 cence of the three distal lateral chambers into a single, wholly or partly mem- 

 branous chamber takes place in all the cases in which an avicularium has not 

 been developed. Hut in addition, the adzooecial, pedal chamber of the daughter- 

 zoa'cium may fuse with the adzoa'cial, infra-scapular chamber of the mother- 

 zoa'cium in the bizoa'cial segment in several Catenaria species, e. g. in Cat. Biiski 

 and Cat. fii.sca. 



As Mac Ciillivray in the genus Sciilicclld speaks of an cpithecas which is 

 generally understood to be a membranous covering over a cryptocyst, I must ex- 

 pressly emphasize, that in this family a cryptocyst only occurs in the form either 

 of the above mentioned, inner calcareous lamina or as an incomplete fdling of 

 the fenestrse of the sternal area. In a series of forms a large part of the surface 

 of the zooccium is indeed covered by a membrane; but in these cases it is the 

 uncalcified external wall of the peculiar lateral chambers, which may in some 

 cases cover the whole of the zocrcial surface, and it might be as justifiable to 

 call the membranous frontal wall in a Fliistra an epitheca in relation to the 

 calcified basal surface. In ail other cases a membrane is completely absent on 

 the calcified surface of the zod'cium. These lateral chambers attain their greatest 

 extent in Struj)hiiiura Ihuvciji (PI. XXI, ligs. (5 a — 6 f), in which they cover nearly 

 the entire surface of the zoa'cium and are only separated by narrow calcareous 

 ridges. They also reach a considerable development in Sciiticella Wilsoni (PI. XI, 

 figs. 2 a— 2 c, PI. XX, ligs. 2 a— 2 b) in Sc. amphora (PI. XI, figs. 3 a— 3 c), Sc. 

 iirniila (PI. XX, figs. 1 a — 1 c, PI. XI, figs. 4 a — 4 b), Calpidiiiin ornalam (PI. XX, 

 figs. 11 a — 11 f) and Cat. ponderosiim (PI. XXI, figs. 5 a — 5 f), in which species 

 they chiefly cover the greater part or the whole of the basal surface. In Sc. 

 Wilsoni (PI. XI, figs. 2 a— 2 c, PI. XX, figs. 2 a 2 b) the greater part of the frontal 

 surface is formed by the infr^-scapular lateral chambers and the entire basal 

 surface by the supra-scapular and the pedal, while the greater part of the basal 

 surface in Sc. amphora (PI. XI, figs. 3 a — .'5 b) is formed by the supra-scapular and 

 the pedal and in .Sc. urniila (PI. XI, figs. 4 a — 4 b) by the supra-scapular, the 

 infra-scapular and the pedal chambers. 



Finally, it must still be remarked that the gonozooecia as well as the keno- 

 zooecia covering the oa'cia may have lateral chambers in varying number and 

 developed to a varying extent, and on the whole these chambers must be said 

 to be of great systematic importance. 



While in a smaller number of the species of this family a distinct sinus is 



