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mere spot, so that this must be regarded as doubtful. In the later 

 paranepionic it is unquestionably propioventran or subventran. In 

 the neanic stage it approximates to and attains an extracentroven- 

 tran position, which it retains throughout life. The position in the 

 gerontic stage was, however, not observed. 



Having had an opportunity for close study of Whitfield's origi- 

 nals and also the fine collection of Mr. Walcott (now in U. S. Na- 

 tional Museum), from same locality, there is but little doubt that 

 the. specific name is correct. 



TARPHYCERAS (?) CONVOLVENS. 



Discoceras convolvens, Angelin et Lindst. (Fragm. Si/., xvi, Fig. 

 3; not PL x, Fig. 5). 



This form has the sutures and similar position of siphuncle and 

 last part of outer whorl free and the lines of growth similar to other 

 species of this genus, as figured on PI. xvi of Angelin and Lind- 

 strom. The figure in section on PI. x, Fig. 5, is doubted, because 

 the whorls appear to be closer coiled and the dorso-ventral diame- 

 ters increase faster than in other specimens figured. 



Eurystomites. 



This genus was first described by Schroder,* who saw that the 

 Nautilus Kelloggi of Whitfield was generically distinct from his 

 genus Estonioceras. He also included in the same genus Nautilus 

 Champlainensis, but this, with Seeleyi and similar discoidal forms, 

 are here placed in the genus Tarphyceras. 



The siphuncle is subventran in the nepionic and ananeanic sub- 

 stages, becoming extracentroventran in all the later stages of devel- 

 opment, or it may remain nearer the venter. The rate of growth 

 of the shell is more rapid than in Tarphyceras and there are fewer 

 whorls in the same diameter. The ventro-dorsal diameters are 

 consequently longer in proportion than in Tarphyceras. The whorl 

 may be rounded until a late stage of development, but usually 

 acquires a more or less flattened venter and primitive lateral zones 

 and ill-defined umbilical zones like those of some species of Tar- 

 phyceras. The lateral zones are apt to be more convergent and 

 the abdomen narrower. 



* Op. tit., Pal. Abh. Dames et Kayser, V, p. 26. 



