1888.] 483 [Newell. 



The siphon is not determined, arid the test is unknown. 

 The general shape of these casts resembles the figure of G. Eos 

 Hall, Pal. Ohio, n, pi. 3. 



Genus PENTAMEROCERAS Hyatt. 

 This genus differs from Hexameroceras in having but five sinuses 

 forming the dorsal aperture. The two pairs of lateral sinuses 

 are arranged symmetrically, as in Hexameroceras, while the fifth 

 sinus is dorsal and occupies a median position, being bisected by 

 the dorsi-ventral plane of symmetry. 



Pentameroceras mirum Barrande. 

 Gomphoceras mirum Barrande, Syst. Sil. Boheme, n, p. 319, pis. 82 and 91. 



This very small species is represented by several casts of the 

 living chamber with a number of closed chambers attached and 

 without the shell. In size and general shape it resembles a con- 

 ical bullet, from which appearance the quarrymen call these fossils 

 " minieballs." 



Comparing these specimens with Barrande's figures on plate 82 

 (above cited) the}' are seen to agree very closely in size and gen- 

 eral outline. The dorsal side is not as flat nor is the ventral side 

 as round as in the specimens figured, the horizontal sections being 

 more nearly circular. In this respect these Indiana specimens 

 stand intermediate between the specimens represented on plate 82 

 and those on plate 91. The last are elliptical in the dorsi-ventral 

 direction. 



The apertures are somewhat obscure but do not differ essen- 

 tially, if at all, from those figured on plate 82. 



The siphon is also similar in size and position, being a mere dot 

 against the ventral side of the shell. 



The septa adjacent to the living chamber are nearer together 

 than those below, indicating as Barrande has pointed out, that 

 these little forms are probably adults. The surface of the shell is 

 not shown. 



Locality. — Delphi, Ind. 



ASCOCERATHXaS. 

 Genus ASCOCERAS Barrande. 

 Ascoceras includes species having a wide aperture, and is thus 

 distinguished from the other Ascoceratidse, which like this have 



