PLATE XLIX—Continued. 
Trematospira MIria, Billings. 
Fig. 21. A dorsal view of the original specimen. 
Lower Helderberg gi-oup. /Square Lake, Maine. 
Genus EHYNCHOSPIKA, Hall. 
Page 108. 
Kitynchospira (?) subglobosa, Hall. 
Fig. 22. A dorsal view of an intei nal cast of the conjoined valves; showing the form of the shell and the 
impression of the hinge-plate. This is the original specimen and its generic relations are net 
fully detei-inined. 
Schohai ie grit. /Schoharie, N. Y. 
Genus TREMATROSPIR.V. Hall 
Page lit 
Trematrospira gibbosa, Hall. 
Figs. 28-26. Dorsal, venti’al, cardinal and frontal views of a large, old anil thickened shell; showing the 
coai'se and sharp plication and jiresenting the usual foj'm of the species. 
Fig. 27. A smallei- example with the median fold and sinus less distinctly developed. 
Hamilton group. Yates county, N. Y. 
Genus PARAZYGA, gen. nov. 
Page ri7. 
Parazyga hirsuta, Htill. 
Figs. 28-32. Dorsal, venti-al, cardinal, frontal and pi-otile views of a normal individual; showing the form, 
contour and line idicalion of the valves. The surface of the shell was covered with short and 
exceedingly tine hair-like spinules which ai-e retained only under the most favorable presei-va- 
tion This is one of the original specimens of the species. 
Fig. 33. A prepaiation, showing, by retnoval 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 {)lates. 
Fig. 35. The interior of a brachial valve ; showing hinge-plate and muscular impressions. 
Fig. 36. A preparation of the bi-achidium, the pedicle-valve and the upper portion of the spiral cones 
being removed; showing the mode of attachment of the crui-a and primai'y lamellae and the 
form 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. 38. The interim' of the rostral region of the ])edicle-valve from which the mai'ginal portion has been 
removed, exposing the short delthyrial or pedicle tube, and remnants of the teeth and dental 
plates. X 3. 
Fig. 39. The cardinal portion of the pedicle-valve; showing the delthyrial tube and the greatly abbrevi¬ 
ated, concave and solid remnants of the deltidial plates. X 3. 
Hamilton group. Various localities in the soft shales of Westei’n Neio York. 
Parazyga Deweyi, Hall. 
Figs. 40-42. Dorsal, profile and ventral views of the miginal 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 poi tion of the brachial valve ; showing the fm-m of the hinge-plate and a short 
median septum. X 3. 
Fig. 44. The same specimen viewed from the cardinal margin ; showing the elevation of the hinge-plate, 
its recurvature and the lobation of its surface. X 3. 
Fig. 45. The intei'ior 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 substance of the shell which tills the entire rostral cavity. X 3. 
Fig. 46. A preparation showing the form of the spiral cones, the position of the loop, the geniculation of 
its lateral branches and the shape of the saddle, (c.) 
Lower Helderberg group (Shaly limestone). The Helderhei'gs, N. Y. 
Genus TREMATOSPIRA, Hall. 
Page 12t. 
Tre.matospira equistriata, sp. nov. 
Fig. 47. A dorsal view of an incomplete shell, similar in form to T. multistriata, but differing from that 
species in the regular, equal, rounded and unbifurcated surface plications. Those in T. miilti- 
striata are not satisfactorily reiu-esented in figures 9 and 10, but are sharper and often strongly 
fasciculate. 
Lower Helderberg group. Cumhes'land, Maryland. 
