386 CAMBKIAN BRACHIOPODA. 



The author states [1868a, p. 100] that this shell can only be described by its external 

 appearance, and that this does not enable him definitely to identify it with Lingula or 

 one of the more recently distinguished genera Lingulella or Obolella. The shell is compressed. 

 The only portion preserved near the beak is about 0.5 mm. thick. Its external surface is 

 marked by somewhat irregularly spaced concentric striae, which are reproduced on the internal 

 cast. Traces of longitudinal striae are shown on the fragment of shell preserved. The shell has 

 a length of 17 mm. and its greatest width is 16 mm. Comparison is made with Oiolella plumbea 

 Salter, of the English rocks, and attention is called to the fact that the English species belongs 

 to the group of the lower Llandeilo, constituting a transition between the primordial and 

 second faunas like the schists of Hof . 



Formation and locality. — Passage beds between the Upper Cambrian, and Ordovician: (303c [Barrande, 1868a, 

 p. 100]) suburbs of Hof, Bavaria, Germany. 



I 



Obolus belli (BiUings). 

 Plate XXXVIII, figures 3, 3a-b. 



Lingula belli Billings, 1859, Canadian Naturalist, 1st ser., vol. 4, pp. 431-432, figs. 7 and 8. (Described and discussed 

 as a new species, as below. The specimens figured by Billings are redrawn in this monograph, PL XXXVIII, 

 figs. 3 and 3a, but it is impossible further to identify BUlings's figures with those in this monograph.) 



Lingula belli Billings, 1863, Geol. Survey Canada, Fifteenth Rept. Progress, figs. 47a-b, p. 124. (No text reference. 

 Figs. 47a-b are copied from figs. 7 and 8, respectively, of the preceding reference.) 



The original description by Billings follows: 



Oval, apical angle about 75°, lateral margins somewhat straight or gently convex for two-thirds of the length, front 

 angles and anterior margins broadly rounded; length one-fourth or one-third greater than the width; greatest width at 

 about one-third the length or a little less from the front. Large specimens are one inch long and nine lines wide, but 

 the usual size is one-third smaller. 



The form so far as regards convexity of the valves is somewhat variable. In general the specimens are strongly 

 convex, or very obtusely carinate from the beak to near the center of the shell, and have three flat slopes, one to each 

 of the lateral margins and one to the front. The most prominent point is a little above the middle, and the anterior 

 slope is always larger than the others. From this form, which is that of a very low three-sided pyramid, with all the 

 angles and edges broadly rounded, there is a series becoming more and more convex, until all trace of the anterior 

 slope is lost, while the two lateral slopes are only visible for a short distance below the beaks. By taking the extremes 

 several species might be made out of this one, but I am satisfied that they would not in the end be sustained. 



The surface is sometimes nearly smooth, but usually it is marked by concentric undulations of growth. I have 

 not been able to detect any minute concentric striae between the larger undulations, and on only one of all the specimens 

 that I have seen are there any longitudinal strise, and these are only faintly indicated on the cast of the interior. The 

 specimens collected in the Chazy limestone in the neighborhood of Montreal are of a jet-black color and often exhibit 

 a polished shining surface, but those in the same rock in the valley of the Ottawa above Carillon are light brown. 



The species is closely allied to L. antiqua (Hall) but is not longitudinally striated. In the Potsdam sandstone on 

 lots 21 and 22, in the 9th concession of the Township of Bastard, L. antiqua occurs in vast abundance, and among 

 the specimens collected at that locality there are a great many which have almost exactly the same foim as L. belli, 

 the only difference being the longitudinal striae. 



I have also before me specimens from the Falls of St. Croix in Wisconsin, said to be L. prima of the Potsdam, and 

 these also have the depressed pyramidal elevation, but are in outline suborbicular or obscurely subpentagonal. The 

 elongated form sometimes referred to L. antiqua appears to me to be L. acuminata (Conrad), and differs from all the above 

 by being convex from the beak all along the median line to the front. 



BiUings [1859, p. 432] has indicated the resemblance of this species to "L. antiqua Hall" = 

 Lingulella (lAngulepis) acuminata (Conrad). In addition, I find traces of the heart-shaped 

 cavity of the ventral valve (PI. XXXVIII, fig. 3a) so characteristic of Oholus and its sub- 

 genera. So far as known to me this is the latest species of Obolus known to occur in any 

 American geologic section. 



The specific name was given in honor of Rev. A. Bell, of L'Original, near Montreal, Canada. 



Formation and locality. — Ordovician: Chazy formation at the following localities [Billings, 1859, p. 432]: 

 (319n) Island of Montreal; (319o) near L'Original; and (319p) on AUumette Island; all in the St. Lawrence River 

 valley, Canada. 



(39211 [Billings, 1859, p. 432]) Limestone of the Chazy formation in the vaUey of Ottawa River, above Carillon, 

 Quebec, Canada. 



