PARALEG0CERA8. 103 



"Wortlieii, but the siphonal saddle is notched l)y a small siphonal lobe, and 

 all the lobes are somewhat constrirtod in the middle. The three external 

 lateral saddles are broadly rounded, while the lobes are sharply pointed. 

 The lobes are eleven in number, three on each side, one on each umbilical 

 shoulder (suspensive lobe) and three intei-n;d, that is, covered bv the 

 involution. The interior lateral lobes and the autisiphonal lobe (dorsal) 

 are very shai-p and lono-. The sutures appi'oach very closely to those of 

 Gastrioceras russicnse Tzwetaev, lint J'arahf/oceras has one more pair of 

 lobes than the Russian species and hfs also a suspensive lobe on the 

 umbilical shoulders. In the latter chai-acteristic Paraleyoceras neivsomi 

 resembles P. tschermjsehewi Karpinsky." Karpinsky * has emended Hyatt's 

 genus to embrace those forms with two lateral lobes and a " suspensive" 

 lobe on the umbilical shoulders. Hyatt ' emended the genus Paralegoceras 

 to include those forms with the second lateral lobe on the umbilical 

 shoulders, and he included in it Gastrioceras russiense Tzwetaev. But the 

 Russian species has the suspensive lobe on the side and has only nine lobes 

 in all, and thus ought to remain in the group characterized as Gastrioceras. 



This species was first assigned bv the writer'' to Paralegoceras iowense 

 Meek and Worthen, although dift'erences were noted. A reexamination of 

 the type and careful comparison with all figures and descriptions of Para- 

 legoceras shows that this form, while nearest to P. iowense, can not correct! v 

 be placed under that species. The umbilicus on P. iowense and on P. neiv- 

 somi is one-fourth of the total diameter. The whorl of P. iowense has a 

 breadth about three-fourths of its height, while on P. newsonri the lireadth 

 is nearly equal to the height. I'he Arkansas species is therefore more 

 globose, with highly arched, helmet-shaped rather than laterally com- 

 pressed whorls, has a much more rapid increase of size of the whorls, and 

 is more involute and less discoidal than P. iowense. 



Shumard's description of P. texanum suggests a near kinship with 

 P. neivsomi, but this form seems to l)e more compressed laterally, more dis- 

 coidal, and more involute than P. neivsomi. Schistoceras missouriense Miller 

 and Faber also resembles this species externall}-, but has one more pair of 

 lobes and saddles, and thus can not be assigned to Paralegoceras. 



nAmmoneen der Artinsk-Stufe, p. 62, PL III, fig. 1. 

 b Ibid. 



c Second Ann. Kept. Geol. Surv. Texas, p. 3.5.5. 

 "Proc. Am. Philos. Soc, Vol. XXXV, p. 263. 



