Descriiotion of Genera and Species. 1 1 



there is no direct attachment to the carapace. Tlie hist trunk segment is not so firmly 

 attached as the rest, and appears to have been slightly movable. Each of these 

 segments bears a pair of similarly constructed biramose limbs identical in structure 

 and function with those of Gnatho/ihausia and bearing similar gills (fig. 7*), and, in the 

 case of the females, similar breeding lamellaj (fig. -6). The bases of the limbs are set 

 wide apart, thus necessitating the wide sternal plates so characteristic of this group of 

 Schizopods (figs. L 3, 5, 7^). Each plate has depressions for holding the sternal 

 branches of the gills which pass inwards from the l;ase of the limbs, but do not meet at 

 the mid-line. A raised triangular area is therefore left with its base abutting on the 

 strengthened anterior margin and its apex in the mid-line near the posterior margin. 

 A median conical boss, hollow within, rises upon this triangular area,' the whole 

 structure doubtless affording attachment for strong muscles. So firm are these sternal 

 plates and arches that they invariably show up through the carapace in flattened 

 specimens in such a manner as to suggest that they were more strongly constructed 

 than the dorsal parts and the carapace combined. In the males, the external genital 

 openings are situated on the sternal part of the last trunk segment, upon papillae 

 which rise out of crateriform pits just behind the insertion of the base of the limbs (fig. 

 7*). 



The carapace (fig. 2), whicli is subquadrate in form, broader behind than in front, 

 with rounded off postero-lateral angles and hollowed out posterior margin, is well arched 

 and covers the backs and sides of all the trunk segments except the dorsal portion of 

 the last one, and is, as already stated, in vital attachment with the anterior ones, but is 

 only loosely folded back over the last seven or eight, and forms with its side lappets a 

 protective covering for the upwardly-directed branches of the gills, as in Gnatliophausia. 

 It is divided into two unequally sized areas by a distinct cervical fold whicli begins 

 at the lateral margins near the antero-lateral angles, and, passing inwards and Ijackwai'ds, 

 becomes V-shaped. The carapace is strengthened by seven longitudinal keels in addition 

 to its thickened lateral and posterior margins. The medi;in or ridge keel is Hanked on 

 each side by a nearly parallel dorso-lateral keel, while tlie four remaining keels, two on 

 each side, are placed not far above the lateral margins, the whole arrangement being 

 almost a counterpart of wliat takes place in Gnathopluitisia. All the keels are inter- 

 ru])te'd by the cervical fold, and some are not carried forward on to tlie area in I'mnt 



'Since writing the aliovc, 1 li:ivc' had tlir cipportunity of e.xaniining n ivniarkalily well preserved 

 specimen liehjnging to !Mr. J. Bowie, showing the ventral aspei-t, wliieli leaves little doubt in my mind that 

 these conical hollow busses held Unninous organs like those found in a similar position on the tail segments 

 of the recent Nicliphanes, witli w hich I have compared them. 



