Hyatt.] 316 [April 4, 



median siphonal saddles which carry the funnel lobes. The de- 

 velopment of the sutures has been followed out by Branco, Sand- 

 berger, and the author, and all agree that these median saddles 

 arise in the centre of the primitive ventral lobes. The two arms 

 of the primitive ventral lobe become widely separated, and appear 

 in the later stages of growth, like true lateral lobes. The first 

 pair of saddles are large and rounded, though in the higher and 

 more involute species, often angular. The ridges from these cross 

 the septa and have corresponding dorsal saddles on either side 

 of the annular lobe. The young are assellate, as first stated by 

 Dr. Branco, and the first sutures and radical forms indicate direct 

 derivation from the same stock as Anarcestes. While still in the 

 broad whorled anarcestian stage, the septa are nautiloidian or 

 concave, but when the deep ventral lobes and large lateral saddles 

 are formed, the septa become ammonitoid or convex along the 

 median line. The funnels, which are also anarcestian in the young, 

 become shortened as the siphonal saddles arise and assume 

 the amrnonitoidal aspect, though no collars are developed. 

 The funnel lobes are variable in size, and may be absent in some 

 specimens, as in two of Gephuroceras lamed in Coll. Mus. Oomp. 

 Zool. This variation has been also observed by Sandberger 

 in this same species and in same variety with one of the above 

 cited instances namely, lamed Var. cordatus, Jahrb. d. Nass. Ver. 

 f. Naturk. Vol. 7, 1851, pi. 3, fig. 21, 22. The early larval sutures 

 have broad dorsal lobes, which become narrowed into annular 

 lobes in later stages correllatively with the development of the 

 ammonitoid septa, and especially with the development of the 

 first pair of lateral saddles. We adopt Beyrich's name of Pri- 

 mordialidae as more significant than that subsequently given by 

 Sandberger. 



Gr3phuroceras, 1 nobis, includes species with discoidal young, 

 whorls with broad and more or less flattened abdomens in the 

 adolescent stages, and the sides divergent as in Manticoceras. 

 There is a decided resemblance to the adults of this genus espec- 

 ially to Man. latidorsatum, but the larval and adolescent stages in 

 the radical species are separable by means of their flattened abdo- 

 men and less rapidly growing whorls. The adult whorls become 



1 r«|>vpa, a bridge. 



