PLATE XLIX— CoDtinaed. 



Trematospira Maria, Billings. 

 Fig. 91. A dora*l view of tho orig-inal 8|>eciineii. 



Lower HeUlei-lHTg' jfi-oiip. Square Lake, Maine. 



Genus RIIYNCHOSPIRA, Hall. 



Page 108. 

 RhYNCHOSPIRA (?) 8UBOLOBOSA, Hall. 

 B1(r- 23. A dorsal view of an iiiteinai cast of tUe uoiijoiiied valves; (ihowiii(^ the form of the shell and the 

 impression of the hinge-plate. This ia the original specimen and its generic relations are net 

 fully determined. 



Schoharie grit. Schoharie, N. T. 



Genus TREMATKOSPIRA. Hall 



Pai?c 124 



Trematrosi'ira oibbosa, Hall. 



Figs. 23-26. Dorsal, ventral, carditml and frontal views of a large, old and thickened shell ; showing the 



coarse and shai-ji plication and jii-esenting the usual form of the species. 

 Vig. 27. A smaller example with the median fold and xiniis less distinctly developed. 

 Hamilton givup. Yates county, N. T. 



Genus PARAZYGA, gen. nov. 



Page 127. 



Parazyga hirsuta, Hall. 



Pigs. 28-32. Dorsal, ventral, cardinal, frontal ami profile views of a normal individual ; showing the form, 

 contour and tine plication of the valves. The .surface of the shell was covered with short and 

 exceedingly fine hair-like spinules which ai-e i-etained only under the most. favorable preserva- 

 tion This is one of the original specimens of the species. 



Fig'. 83. A prepai-ation, showing, by removal of the brachial valve, the form of the spiral cones and their 

 attachment to the crura. 



Fig. 34. The interior of a pedicle-valve ; showing the character of the muscular area and the concave del- 

 tidial plates. 



Fig. 35. The interior of a brachial valve ; showing hinge-plate and muscular impressions. 



Fig. 36. A pi-eparation of the bi-aihidium, the i>ed!cle-valve and the upper portion of the spiral cones 

 being removed J showing the mode of attachment of the crura and primary lumellse and the 

 foi-m of the loop. The hinge-plate is not correctly represented. X 2. (c.) 



Fig. 37. The hinge-plate enlarged ; showing its bipartite form and the broad dental sockets. X 3. 



Fig. 88. The inferior of the i-oslral region of the pedicle-valve from which the marginal poi-tion has been 

 removed, exi>osing the short delthyiial or pedicle tube, and remnants of the teeth and dental 

 plates. X 3. 



Fig. 39. The cardinal i)ortion of the pedicle-valve ; showing the <lelthyrial tube and the greatly abbrevi- 

 ated, concave and solid remnants of the dellidial plates. X 3. 



Hamilton group. Variotts localities in the soft shales of Western New York. 



Parazyga Deweyi, Hall. 



Figs. 40-42. Dorsal, profile and ventral views ol the «i iginal specimen ; showing the form of the shell. In 

 figure 40 the brachial valve is represented as too flat medially, there being a low fold to cor- 

 respond with the sinus on the opposite valve which is shown in tig. 42. 



Fig. 43. The interior of a portion of the brachial valve ; showing the form of the binge-plate and a short 

 median se|)tum. X 3. 



Fig. 44. The same specimen viewed from the cai-dinal mai-gin ; showing the elevation of the hinge-plate, 

 its recurvafnre and the lol)ation of its surface. X 3. 



Fig. 45. The interior of a portion of the pedicle-valve ; showing the concave and solid deltidial plates, 

 coalesced only at their anterior margin, and the recurved teeth. The deltidial plates are con- 

 tinuous with the sub.xfance of the shell which fills the entire rostral cavity. X 3. 



Fig. 46. A preparation showing the form of the spiral cones, the position of the loop, the geniculafion of 

 its lateral branches and the shape of the saddle, (c.) 



Lower Uelderbei-g group (Shaly limestone). The Helderbergs, N. Y. 



Genus TREMATOSPIRA, Hall. 



I'aRe 121 



Trematospira kquistriata, sp. nov. 



Fig. 47. A dorsal view of an inromplete >\f\\. similar m form to T. vmltistriata. Imt diffei-ing from that 

 species in the reguUr, t-qual, rounded and unliifurcated surface pliialions. Those in T. iniUti- 

 Ktriata are not satisfactorily represented in figures 9 and 10, but are sharper and often strongly 

 fasciculate. 



Lower Helderberg group. Cumberland, Maryland. 



