FOSSILS OF THE CLINTON GROUP. 539 



the next species. A much better specimen occurs in the collection of 

 Mr. Geo. Caswell; it was found at the type locality, Soldiers' Home. 

 Plate 35, Fig. 1. A second specimen in Mr. Caswell collection has more 

 distant septa. Plate 35, Fig. 2. 



OrtJioceras (Actinoceras) Daytonense, Foerste. 



(Plate 33, Fig. 6.) 



This species, described from Soldiers' Home (Proc. Boston Soc. 

 Nat. Hist., 1889) has a broadly annulated siphuncle and rather close 

 septa. 



OrtJioceras {Eu-OrtJiocerasf) rectum, Worthen, var. Junius, Foerste. 



(Plate 32, Figs. 1, 2.) 



The very low rate of increase of diameter in this shell and its very 

 distant septa are the only features known at present which will serve to 

 characterize this species. (Proc. Boston Soc. Nat. Hist., 1889.) The 

 siphuncle and surface have not been seen. 



OrtJioceras {Eu- OrtJioceras) ignotum, Foerste. 



(Plate 32, Fig 4 ; Plate 36, Figs. 6, a, b, c ; Figs. 5, 6, 7. Page 540 ) 



The type specimen was found at Hanover, Indiana. On re-examina- 

 tion it appears that the figure published Proc. Boston Soc. Nat. Hist., 1889 

 (See Plate 32, Fig. 1, of this volume) represents the divisions of the si- 

 phuncle distinctly contracted at both ends towards the septa, whereas they 

 are in reality almost cylindrical, enlarging very slightly towards the upper 

 septum in each case, and contracting suddenly before passing through the 

 septum. The same form is found in the upper shaly courses at Huffman's 

 Quarry. Fragments of the same individual were found which, when added 

 together, gave a length of more than 180 mm. One of these fragments, 

 59 mm. long, was 17 mm. broad at the upper, and 13 mm. at the smaller 

 end, and contained in this length 16 septa. Another fragment, 47 mm. 

 long, contained in this length 12 septa, and at its upper extremity where 

 the diameter was 20 mm. the almost cylindrical siphuncle was 2.3 mm. 

 broad. In another specimen 35 mm. long, with 10 septa, 20.5 mm. 

 broad at the upper extremity and 17 mm. at the lower, the siphuncle 

 was 2.8 mm. at the larger end. The divisions of the siphuncle between 

 the septa were almost cylindrical, showing only a trace of convexity in 

 longitudinal sections. This last specimen showed a thin shell .25 mm. 

 thick. It was perfectly smooth. Its septa described an arc of 100° in 

 cross-section. Another specimen 23 mm. long, with the diameters at the 

 ends 17 and 15 mm. respectively, shows 7 septa, and the cylindrical 

 siphuncle is 2.1 mm. wide;- the shell is thin and smooth. (See 



