44 PALJEONTOLOGY OF NEW YORK. 



but probably serving as a faunal equivalent of the Niagara and Guelpb forma- 

 tions. No species are known in Great Britain, those from the Island of Got- 

 land, and from Livonia, Russia, are from faunas corresponding to that of the 

 Niagara and Wenlock. 



"to^ 



Genus RHINOBOLUS, Hall. 1871. 



PLATE IV B, FIGS. 7-li. 



[?] 1862. Obolus, Billings, Palsenzoic Fossils, voL i, p. 168, fig. ISl. 



1871. Trimerdla, Dall. American Journal of Conchology, vol. vii, p. 83. 



1871. lihynoholus, Hall. Advance .sheets (March) Twenty-third Rept. N. Y. State Cab. Nat. Hist., p. 



247, pi. xii, fig. 10. 1873. 

 [1] 1871. Obolellina, Billings. Canadian Naturalist, vol. vi, New Series, p. 220 (Decembei-). 



1872. Dinoholus, Davidson an<l King. Report Brighton Meeting of Bi-itish Association. 



1874. Trimerella (.'), Davidson and King. Quart. Journ. Geological Society, vol. xxx, p. 151, pi. xviii, 



fig. 13 ; pi. xix, figs. 4, 4a. 

 [?] 1884. Rhynoholus, WiirrEAVES. PalaBozoic Fossils, vol. iii, pt. I, p. 7, ]>!. ii, fig. la; pi. viii, fig.s. 3, 3a. 



Diagnosis. General form of the shell as in Trimerella. 



Pedicle-valve, in the typical species, with an elevated, solid beak, having a 

 broad and high deltidium, divided into a relatively narrow central area (which 

 may be concave or convex), and broad deltidial ridges. Crescent and terminal 

 scars as in Trimerella. Umbo-lateral scars sharply defined. Platform very low 

 and incompletely developed, consisting of a broadly V-shaped elevation, with 

 a raised anterior margin, and surface sloping abruptly backward to, or even 

 below the general curvature of the internal surface. A faint longitudinal sep- 

 tum extends forward from the platform. 



Brachial valve with low, sub-marginal, slightly curved apex, and short delti- 

 dium. Crescent conspicuously developed. Platform as in the opposite valve, 

 with the addition of a central scar, which gives the entire area a tripartite 

 appearance. Median septum faint. 



Type, ''Rhynoholus .? " Hall. (1871, loc. at., pi. xii, fig. 10.) 



Observations. The description of the genus Rhinobolus (erroneously printed 

 Rhynobolus) was based upon the interior of a pedicle-valve, characterized as in 

 the foregoing diagnosis. At the time of the publication of the generic term, 

 this valve had not been positively identified with the Obolus Galtensis olVtiWmg?, 



