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University of Texas Bulletin 



type individual (pi. 2, fig. 1) in which the ribs are at some places evi- 

 dently branching, and at other places apparently of alternate length. 



The remaining visible portion of the coil shows in general an alter- 

 nation of one branched with one unbranched rib. This alternation is 

 often irregular ; in pi. 2, fig. 8 the simple ribs preponderate. The branch- 

 Jng may be incipient giving the impression of an alternation of one 

 branched rib with two simple ribs or of one long simple rib alternating 

 with two short simple ribs (pi. 2, fig. 12) . In one individual (pi. 2, fig. 12) 

 a branch from a principal rib at one umbilical margin crosses the venter 

 and fuses with the next principal rib, giving a zig-zag ribbing. 



Briefly the ribbing is more branched on the coil and simpler' on the 

 straight portion. It is seen that the ornamentation of the coil somewhat 

 resembles that of S. meslei Grossouvre (Coniacian), which, however, has 

 the principal ribs more prominent and the secondary ribs largely un- 

 branched; this species also unrolls much less rapidly than the type of 

 S. hilli. The obesity of the typical S. hilli also removes it from S. obliquus 

 as does the coarseness of its ribbing; in fact, no individual known ap- 

 proaches S. obliquiis in either respect. In both respects it is similar to 

 the thick coiled examples of S. aequulis Sowerby, from which it differs 

 in the rate of increase of its turns, in the dorso-lateral tubercle and shape 

 of the umbilicus, and in the suture. S. aequalis shows the same prom- 

 inence of the primary ribs near the umbilical margin and the same branch- 

 ing laterally on the coil, as S. hilli. 



Fig. 6. Scaphites hilli Adkins and Winton, suture, type individual, camera lucida 

 drawing, x 12. The fossil is figured on PI. 2, fig. 1. 



SUTURE: Figure 6 shows the suture of the type, so far as can be 

 seen without dismembering the scaphite. This well developed suture has 

 externally besides the siphonal lobe, two conspicuous lobes and near the 

 umbilical wall a third irregular, low, wide lobe. Of these, the first lateral 



