920 THE PALEONTOLOGY OF MINNESOTA. 



IHellerophon recurvus. 



BELLEROPHON RECURVUS, n. sp. (Ulrich.) 



PLATE LXIV, FIGS. 11-13. 



This species is closely related to and in some respects intermediate in position 

 between B. clausus and B. similis. The lines of growth curve backward as in the 

 latter, while the umbilicus is entirely closed as in the former. Compared with B. 

 clausus we find that the lines of growth curve backward much more strongly in 

 approaching the dorsal carina, and the outer lip consequently has a much deeper 

 sinus, while the callosity of the inner lip is not so great. The aperture, as nearly 

 as we can make it out, must be very much as in B. troosti (pi. LXIV, fig. 3), not so 

 much expanded laterally perhaps. The absence of an umbilicus will distinguish 

 the species at once from B. similis. None of the other known Lower Silurian 

 species of the genus are as closely related as the two with which wo have compared 

 B. recurvus. Further remarks are, therefore, unnecessary, particularly since it is our 

 wish that the student should rely chiefly upon the illustrations in seeking to identify 

 the species of this difficult group of fossils. 



Formation and locality. So far known only from the Loraine group at Cincinnati, Ohio, where 

 a few specimens were found near the tops of the hills. 



Colkction. E. O. Ulrich. 



BELLEROPHON SUBANGULARIS, n. sp. (Ulrich.) 



PLATE LXIV. FIGS. 14-16. 



Having no umbilicus, this species is related to B. clausus and B. recurvus, but it 

 is distinguished at once from both by its subangular dorsum, and relatively narrower 

 and somewhat triangular aperture. Its surface markings are rather distinct and 

 regular; on the dorsal slopes they sweep backward gently to the carina. 



Formation and locality. Richmond group, Richmond, Indiana. 

 Colkction. E. O. Ulrich. 



BELLEROPHON MOHRI Miller. 



PLATE LXIV, FIGS. 44 and 45. 



Shell large, last volution with the aperture abruptly and greatly expanded 

 laterally; inner volutions of moderate size, appearing rather closely involute, having 

 only a small umbilicus, with the slope on each side of the carinated dorsum slightly 

 flattened; aperture somewhat semicircular in outline, much wider than high, its 

 width comparing with the hight of the entire shell about as seven to ten; outer lip 

 thin, the small V-shaped central emargination prolonged backward into a rather long 

 narrow slit, which as growth continues forms the slit-band; inner lip thick, greatly 



