FOSSILS OF THE CLINTON GROUP. 533 



proprius, Hall, these forms are only young stages of species whose sub- 

 sequent growth becomes' free and more erect cannot be determined with 

 the material at hand. 



In a second specimen from Brown's quarry, the same habit of shell 

 was noticed; it started its growth attached to theside of Platyceras, curved 

 around on its surface, attached to it along one side, and then, swinging 

 loose from the Platyceras, assumed a straight course for the rest of its 

 growth. The straight species also occurs at Pennsylvania, as collected 

 by Prof. E. W. Claypole, from the top of the Clinton just under the 

 red Onondago shales, near Mifflintown, Juniata county, Pennsylvania. 



Gomphoceras Ortoni, sp. nov. 



(Plate 33, Pigs. 8 a, b ; Plate 36, Fig-s 7 a, b, e. ) 



In the Proc. Boston Soc. of Nat. Hist., 1889, Plate VIII, fig. 8, was 

 represented the living chamber of a species of Gomphoceras found at 

 Brown's Quarry (See Plate 33 of this volume). Recently the specimen fig- 

 ured has been better cleaned from the encrusting calcite and though in the 

 form of a' cast of the chamber its configuration can now be better deter- 

 mined. The living chamber was-contracted towards the top and bent a 

 little backwards so that the posterior side is slightly concave in outline 

 about 17 mm. above the base of the chamber. The various intricate 

 markings towards the aperture caused by flexures of the shell will be 

 better undersood by a reference to the figures than by a detailed descrip- 

 tion. 



At the same quarry was found a specimen with the living chamber 

 only indifferently preserved, but almost the entire septate part of the shell 

 is shown, thus adding considerably to our knowledge of this species. 

 The specimen belongs to the collection of the Ohio State University. 

 At the base of the body chamber the shell is 30 mm. broad. Measuring 

 along the sides of the shell, the fifth septum below this point is 16 mm. 

 distant, and the septum has a diameter of 22 mm. The tenth septum 

 below the body chamber is 28 mm. distant and the diameter of the sep- 

 tum is 14 mm. The fifteenth septum below is 38 mm. distant and the 

 septum has a diameter of 9 mm. The twentieth septum is 47 mm. dis- 

 tant; this portion is less well preserved, but the diameter does not seem 

 to have been less than 8 mm. In other words, after a rather low rate of 

 expansion, the shell expanded rapidly up to within three chambers of the 

 living or body chamber, after which the rate of increase was again very 

 small. A fragment of some Gomphoceras' found in the upper shaly 

 courses at Huffman's Quarry, consisting of two chambers only, is referred 

 to the same species, on account of its similar rate of expansion at a cor- 

 responding diameter of the 'shell. Of course this determination is 



