72 G. E. Beecher — Development of Shell in Tornoceras. 



The specific limits of T. uniangulare have not been clearly 

 defined, and many of the forms referred to Parodiceras (Gon.) 

 discoideum Hall, are evidently of the former species. A 

 comparison of the type specimens of both with others 

 which have been grouped with them, as figured in the 

 Thirteenth Report, New York State Cabinet, and in vol. v, pt. 

 ii, of the Palaeontology of New York, shows that the first 

 species is really the common one, and so far as known, the 

 second is represented only by the original types.* 



The adult differences are mainly noticeable in the depth of 

 the air chambers, and in the sutural curves. They can readily 

 be determined by strictly limiting the characters to those first 

 ascribed to each species. Parodiceras discoideum is also 

 apparently without the narrow cone at the bottom of the 

 annular lobe, and the ventral saddle is much less depressed. 



The material for this paper is a portion of a collection pre- 

 sented to the museum of Yale University, by Thomas G. Lee, 

 M.D. The particular lot containing the Tornoceras consisted 

 of several hundred nodular concretions of pyrite of a radiated 

 structure, obtained from the Devonian (Hamilton) shales of 

 "Wende Station, Erie County, New York. Most of them 

 preserved an organic nucleus, and about twenty-five species 

 have been identified as belonging to the Trilobita, Cephalopoda, 

 Pteropoda, Pelecypoda, Brachiopoda and Crinoidea. 



The test of the trilobites and the shells of the brachiopods 

 are but little altered, while those of the cephalopods and 

 pelecypods are usually replaced by sphalerite, a difference 

 evidently connected with the more soluble nature of the 

 pearly shells of the nuculoids and cephalopods. 



By carefully breaking away the outer enveloping volutions 

 of a number of specimens of Tornoceras, the early parts of 

 the shell were uncovered, and found to be well preserved, and 

 therefore, suitable for study. The drawings on Plate VIII 

 were made from the microscope, with a camera lucida. 



The protoconch (figures 1, 2, Plate I) has an axial diame- 

 ter of about l'l mm and varies but little from this dimension 

 among several specimens measured. The vertical diameter is a 

 little shorter, so that the general form is that of a prolate 

 ellipsoid. The latera are prominent, and exposed as central 

 bosses in the umbilicus of a young shell. 



* The following list is proposed as corrected references to T. uniangulare : 



13th Ann. Rept. X. T. State Cab., p. 98, figs. 6 (bis) (type specimen) and 6 ? 



Pal. N. T., vol. v, pt. ii, pi. 71, figs. 11-14 (fig. 14= type specimen), pi. 72, figs. 

 6, 7, pi. 74, figs. 2, 4., vol. vii, pi. 127, figs. 10, 11, 12. 



Of these, pi. 71, figs. 11. 12, 13 ; pi. 74, fig. 4 and pi. 127, figs. 11, 12, were- 

 referred to P. (GonioMtes) discoideum. Hall. 



