50 
GEOLOGY 
only by a division of the strias, that simple at their origin, soon subdivided into throe, which are continued to the 
margin without further division; this one has been named Sp. Iriplicala^aW. But on studying a considerable number 
of specimens, it becomes apparent that they pass insensibly from one of these species to the other, and that in 
fact there is only one, the true Sp. slrialus with the varieties Iriplicalus (See: Paleontology of The Exploration of the 
Great Salt Lake, by Capt. Stansbury, p. 410.) and Owenii (See: Illustrations to the Geological Report of Wisconsin, 
Iowa, and Minnesota, by D. D. Owen; plate V, fig. 4; under the name of Sp. fasciger? Philadelphia, 1852.). 
The Sp. fasciger of Keyserling (See: Wisscnschafllicke Beohachlungen auf einer Reise in das Petschora-Land , im 
Jahre 1843, pag. 231; pi. VII , fig. 3. 3 a, 3 b. S* Petersburg, 1846.) is a good species, different from the Owenii 
variety of the Sp. slrialus^ although it has some resemblance to it. Mr. de Koninck writes to me that he considers 
the Spirifer Condor of d’Orbigny (See: Paleontologie du Voyage dans VAme’rique Me'ridionale , p. 46; pi. V, fig. 11 — 14. 
Paris, 1842.) as a variety of Sp. strialus. 
Locality. — The Sp. striatus var. triplicatus and Sp. strialus var. Owenii are abundant in the Rocky 
mountains, especially at Pecos village, at Tigeras, on the summit of the Sierra de Sandia, at 
Great Salt lake, and at Vancouver island. 
Explanation of figure. — Plate VII , fig. 3. Front view of specimen from Pecos village. 
SPIRIFER ROCKY-MONTANI n- sp. 
Plate VII , fig. 4 , 4a, 4b, 4c, 4 d , 4 e. 
Description. — Shell transverse, gibbous, subsemi-circular , length and breadth nearly equal, cardinal angles 
rounded. Beak large, elevated, incurved; hinge line shorter than the width of the shell, straight. Sinus of the 
dorsal valve shallow, extending from the beak to the margin, covered with ribs, like the other parts of the two 
valves. The ribs are simple, sharp and very distinct. Area small and triangular. The lines of growth are indis- 
tinct on the two valves. 
Observations. — This species slightly resembles in form the Sp. rotundatus Mart. (See: Fossiles du 
Carbonifere de Belgique, by de Koninck; p. 263; pi. XVII, fig. 3, 3 a, 3 b, 3 c.), but it differs in hav- 
ing a smaller sinus covered by the ribs, while the Sp. rotundatus has larger and less numerous ribs, 
and the sinus is without any. 
Locality. — I found this beautiful species in the Mountain Limestone of Tigeras, Canon of San 
Antonio , New Mexico ; where it is not rare. 
Explanation of fgures. — Plate VII, fig. 4, 4 a, 4 b. Different views of a large specimen. 
» VII, fig. 4 c. 4d, 4 e. Young shell a little compressed. 
SPIRIFER LIXEATFS Mart. 
Plate Vil, fig. 5, 5 a, 5 b, 5 c. 
Description. — Shell transversely oval, moderately convex, hinge line half the width of the shell ; beaks appro- 
ximate; cardinal angle and sides semi-elliplically rounded; no sinus in front; margins in one plane. Cardinal area 
low , triangular , no trace of mesial fold. Surface of both valves covered with subregular concentric lamella}; some- 
times marked with a row of strong longitudinal notches , producing a very delicate imperfect reticulation. 
Locality. — This Species, so common in Europe (See: PaUontologie de la Russie et de VOuraL^ 
by de Verneuil; p. 147; pi. VI, fig. fi , 6 a, 6 b.), is also found in the Rocky mountains. I found 
it at Pecos village and at Tigeras, where it is not very common. 
Explanation of figures. — Plate VII. fig. 5 , 5 a , 5 b. Different views of specimen from Pecos. 
» VII, figure 5 c. Specimen from Tigeras, showing to the naked eye the 
reticulation of its surface. 
TEREBRATULA ROCKY-MOXTANA n. sp. 
Plate VI, fig. 13, 13 a, 13 b, 13 c. 
Description. — Shell reniform , sub-triangular, depressed convex; beak sharp and pointed; sinus very wide and 
shallow , furnished with two or three longitudinal ridges ; no lateral ribs. Surface smooth. 
