1883.] 825 [Hyatt. 



shaped with more complicate:! lobes and saddles like Monophylli- 

 tes, Ceratites Sturii, Dinarites M:>hammedanu3, and the le3S invo- 

 lute, smooth, similar, form? of Gymnites, Pfcychites, perhaps also 

 Pinacoceras, and Ophiceras begin to be more numerous and to 

 replace the Paleozoic radicals as generators of distinct genetic 

 series. Psiloceras, though in the Jura, belongs, we think to this 

 class of radical forms. 



The tertiary radical forms of the Jura and Cretaceous are often 

 highly ornamented and complex in their sutures, but they are also 

 discoidal, like all other larval radicals and they give rise to pro- 

 gressive series of more involute forms as we have tried to demon- 

 strate in several families, and numerous genera. Following out 

 Hackel's nomenclature which we regard as truthful and express- 

 ive, these categories of radicals can be very appropriately desig- 

 nated as the Epacmatic, and Acmatic radicals, and when as is often 

 the case, the Acmatic forms become the radicals of degenerative 

 series of uncoiled forms, we propose to call them Paracmatic 

 radicals. 



[Gastriocerae.] 



Brancocsras, 1 nobis, includes species of the Devonian and 

 Carboniferous with undivided, ventral lobes, rounded or spatulate 

 first pair of saddles, broad, abrupt, magnosellarian saddles, and 

 only one pair of often hastate lateral lobes. The spheroidal 

 form of the shell, the deeply involute, and semilunar whorls show 

 close affinities for Parodiceras. The adult stages still continue to 

 have the septa concave along the centre, and only convex in the 

 region of the magnosellarian saddles. The annular lobes are large 

 and undivided, and the first pair of saddles have corresponding 

 saddles on the dorsum. The dorsal sutures have also large 

 saddles corresponding to the magnosellarian saddles as in the 

 Magnosellaridae and three lobes. The internal sutures are, 

 therefore, precisely similar to those of Sporadoceras, but the 

 external sutures have one pair less of lobes and saddles, and in 

 that genus the first pair of saddles on the venter have no corre- 

 spondents on the dorsum. The closest connection evidently ex- 

 ists between this genus and Munsteroceras, which have similar 

 outlines in the sutures, and rounded first lateral lobes as in this 



l Dedicated to Dr. W. Branco. 



