1883.] 307 [Hyatt. 



the most important fact of the embryology of the ISTautiloids, the 

 cicatrix, and failed in correlating the resemblances between the 

 embryos of Nautiloids and Ammonoids, and in correctly distin- 

 guishing their differences. 



We appreciate his work very highly, and we gladly acknowl- 

 edge discoveries properly belonging to him, and these are, the 

 distinctions of the Asellate, Latisellate, and Angustisellate types 

 of embryo among Ammonoids. The progression of the embryo 

 through the concentrated and accelerated inheritance of ancestral 

 characters was previously stated by ourselves, and his remarks on 

 this point are simply confirmatory, though more fully stated, 

 more completely worked out, and more richly illustrated. 



Goniatitinae. 



This sub-order may be characterized by the possesion of smooth 

 shells marked principally by transverse striae, and open aper- 

 tures similar to those of Nautiloidea. The large ventral sinuses 

 of the apertures of nearly all the species show, that they must 

 have possesed powerful hyponomes, or fleshy ambulatory funnels, 

 and were animals which had similar habits to those of Nautiloids, 

 capable of crawling efficiently on the bottom or of swimming 

 by the use of the hyponome. The sutures are entire, with a few 

 notable exceptions, in the later forms. The funnels change from 

 the macrochoanitic form to a short transitional form, and in some 

 species in later formations acquire the true ammonitoid collar, 

 or in other words, become completely cloiochoanitic. 



The ventral lobes are undivided, and similar to simple funnel 

 lobes only in the Nautilinidae and Magnosellaridae. In the 

 remaining families genera may have undivided or divided ven- 

 trals in the same family, or exclusively divided ventrals as in the 

 Primordialidae. The dorsal or inner sides are occupied by sad- 

 dles only in the gyroceran form, Mimoceras, and the uncoiled or 

 gyroceran larvae of higher forms. The Nautilinidae have a broad 

 dorsal lobe in the impressed zone, but no annular lobes except in 

 one genus, Agoniatites. All the remaining genera have annular 

 lobes, so far as known, except the transitional species from 

 Anarcestes to the Magnosellaridae included in the genus Parod- 

 iceras. The annular lobes are undivided so far as known, the 

 true siphonal saddles having no corresponding dorsal saddles as 



