BULLETIN OF THE LABORATORIES 
Il8 
ly longer, or more elliptical ; length of the outer chamber not deter- 
mined. Septa concave — six chambers occupying a length of lo mm. 
in the specimen above mentioned. Siphuncle eccentric, nearer to 
the centre than to the margin, narrow at the septa, expanding within 
the chambers. 
Surface apparently not preserved, specimens in the form of casts. 
There are indications of longitudinal striae, preserved with various de- 
grees of distinctness, in some worn specimens looking like rows of 
small pits. Along one side of the shell, nearest the position of the 
siphuncle is a narrow, raised, longitudinal line, laterally defined by 
grooves which more or less coalesce anteriorly towards the annular rings 
(septa), and thus produce interruptions along the line. The distinct- 
ness of this longitudinal line is extremely variable, or perhaps is due to 
the removal of some of the surface matter, because some of the best 
preserved specimens are smooth, whereas those which are worn are apt 
to present these features. ( Cf. O. jDuseri, Hall and Whitfield . ) 
Locality and position. Beavertown marl, Clinton Group. A speci- 
men in the Ohio State collection, from Wilmington, Ohio, I refer to 
this species. 
Expt.anation of Plates. 
Plate XIII. 
Fig. I. Orthoceros inceptuni, n. sp ; a, lateral views b, views showing the 
position of the siphuncle ; c, vertical section through the siphuncle. 
Fig. 2. Aleristella iimbonata, Billings (sp ); a, lateral view; b. dorsal valve. 
Fig. 3. Flatyostonia Niagarense. Hall; a, b, specimens referred to the Ohio 
forms considered identical with the Indiana species, having the aspect of Holopea. 
Fig. 4. Eichwaldia reticulata. Hall; a, dorsal valve ; b, ventral valve. 
Fig. v Leptccna prolongata, n sp.; a, ventral valve; b, lateral view, outline. 
Fig. 6 . Zygospira inodesta, Say (sp ); dorsal valve. 
Fig. 7. Ortliis biforata, var. lynx ( Von Buck), forma reversata; ventral 
valve. 
Fig. 8. Orthis biforata, var. lynx ( IPn Bitch), forma Daytoncnsis; ventral 
valve. 
Fig. 9. Atrypa nodostriata. Hall; ventral valve. 
Ing. 10. Ortliis hybrida, So^ivcrby; a, dorsal valve ; b, lateral view, drawn for 
the outline only. 
Fig. II. Orthis elegantula,_ Dalinan; a, dorsal view; b, lateral view, drawn 
for the outline only. 
Fig. 12. Orthis fiabella, Sowcrby; a, ventral valve; b, dorsal valve. 
Fig. 13. Orthis Daytoncnsis, n. sp.; a, dorsal valve ; b, lateral view, drawn for 
