LOWER CARBONIFEROUS FOSSILS. 519 



form; the branches are thin, straight, and parallel, and the bifurcations 

 infrequent. The other species is finer, more delicate, and very irregular. 

 The material at this locality is preserved as red ferruginous impressions in 

 an ocher-coiored argillaceous limestone, and no details of structure could 

 be ascertained. 



At the head of Conant Creek, Teton Range, Fenestella is the most 

 common fossil present. It is preserved chiefly as casts in a hard, whitish 

 limestone, and two species can probably be distinguished. The first is 

 very regular in growth and attains large size. One incomplete fragment 

 is 5.5 cm. across. The dissepiments and branches are nearly equal in size, 

 the fenestrules oval or subcircular. Measuring radially, there are ten or 

 eleven fenestrules ill 10 mm., and sixteen or seventeen measuring trans- 

 versely. There are three cells opposite each fenestrule. Another probably 

 distinct species is quite similar in general appearance, but more delicate 

 than the last. Fenestrules nearly circular, eighteen or nineteen occurring 

 in a radial direction of 10 mm., and twenty-five or twenty-six in the same 

 distance measured at right angles to the first. 



Another species is found in bed 28, Crowfoot Ridge, Gallatin Range. 

 The frond is quite regular, branches the same size as the dissepiments. 

 The fenestrules are long, elliptical, eleven or twelve in 10 mm., radially 

 measured, and seventeen in transverse direction. Twelve or thirteen zooecia 

 are found opposite four fenestrules (thirty-four to thirty-six in 10 mm.). 

 Another type, from the top of bed 24, Crawford Ridge, Gallatin Range, 

 is perhaps specifically related to the last. It is somewhat coarser, with 

 stronger branches and dissepiments. Fenestrules oval, about nine in 10 mm. 

 radially and fifteen or sixteen transversely. Eleven to thirteen zocecia 

 opposite three fenestrules (about thirty in 10 mm.). 



ARCHIMEDES Lesueur, 1842. 



Archimedes sp. 



The axis of this form has not been observed, but the peculiar manner 

 in which the branches overlie one another can not be mistaken, and makes 

 the generic reference certain. It has not been possible to make sufficiently 

 detailed observations on which to base a specific description. The branches 

 are rather slender, not frequently bifurcating, about twenty-six in the space 



