TABLE IV. 



FOSSIL COKALS, FK05I THK CAEBONIFEEOUS EOCKS OF IOWA. 



Tub. IV., Fig. 1. Rctcjioi a Archuncdes, hom beds /,* near tlie top of the Lower Series of Carboniferous Limestones, Keokttli 

 Rapids of the Mississippi. 



" " a. Magnified view of a portion of the reticulated screw-Hlie expansions of the coral, showing the form 



and distribution of the fenestrules, interstices, and dissepiments. 

 This reticulated fossil coralline has a wide geographical distribution in rocks of this age in the Western 

 • ^ States of North America. It has been known to Western geologists for many years under the name of 



( Archimedes. Lesueur prepared drawings of this fossil before he left this country finally for France, 



. • doubtless with the intention of publishing a description of it ; but never did so, to niy knowledge. I 



gave a figure of it, in 1842, in an article which I prepared for Silliman's Journal, ''Regarding Human 

 Foot-marks' t in the Carbonifei'ous Limestone of the Mississippi, and stated that it seemed to be a 

 species of Retcpora coiled in the shape of a screw. Il' the reticulated species of corals which have 

 usually been referred to this genus really are distinct from Gorgonia, then it belongs doubtless to the 

 genus Retepora. De Koninck, in his work descriptive of the carboniferous fossils of Belgium, says it is 

 exceedingly difficult to distinguish fossil Gorgonia from Rclcpora, as the distinction lies merely in the 

 absence or presence of a cortical investment, which in fossils is seldom preserved ; and he refers all his 

 • carboniferous fossils, possessing a similar structure to this coral, to Gorgonia, because he says that Gold- 

 fuss has undoubtedly detected a cortical investment in Gorgunia rcpisteria, and infers that all its con 

 geners, of an analogous structure, have a similar organization. If this be so, it is possible that the 

 Archimedes may be a screw-shaped Gorgonia. 

 " Fig. 2. Cyaihophylluin (vermiculare ?) Goldfuss. It is with some hesitation that I refer this coral to the above 

 species, since some of its characters are certainly distinct from that species, as given by Goldfuss. Neither 

 at the knee-like flexions, nor elsewhere on the external surface, are the margins of the cells visible, 

 but only annular swellings continuous with the general surface of tlie coral. The terminating cell is 

 shallow, oblique, with about forty-five lamelhie radiating straight from near the axis to the circum- 

 ference, where faint, short, intermediate lamella^ can sometimes be observed. Coral bent at intervals, 

 and at the same time slightly twisted on its axis ; almost cylindrical, or very slightly conical. 

 Dimensions, about five inches long, and half an inch in diameter. 



It occurs in the Carboniferous Limestones, near the moutli of Keg Creek, associated with Chonctes variolata. 



If it be new, as is very probable, I propose for it the name of C. torqiiium. 

 " Fig. 3, a, b. Cijathophyllum Jlc.xuosum (T), from near the mouth of Keg Creek. 

 " Fig. 4. Cyathophyllum [fungiics?) (Flem.), from tlie Keokuk Rapids of the Mississippi. 

 " Fig, .5. Lit hostrot ion basaltiforme (^Siylina of liesvem). 



" " a. Dissected cell-tube, showing the external walls, the irregularly arched cellular structure between them 



and the core ; the internal structure of the latter with its arched partitions and styloid axis. From 

 bed d' of the Upper Series of Carboniferous Limestone, Sweet Home, on the Des Moines River. 

 This honeycomb-like coral is remarkably characteristic of member d' of the Upper Series of Car- 

 boniferous Limestones of Iowa, and indeed prevails in the same geological position all over the 

 Western States. As early as 1832, Lesueur figured this fossil under the name of Stylina, by which 

 name it was long known to Western geologists. Its internal structure seems to correspond very 

 nearly with the description given by Keyserling, p. 152, of the Lithostrotion, as it occurs in the 

 Southern Urals. The coral is made up of groups of nearly parallel polygonal prisms, mostly five-sided, 

 but some four- and six-sided. Each prism is composed of simple external walls (5, a), a thick core, 

 and an axis. Between the external walls and core are funnel-shaped, plicated lamellse, which blend 

 into both, and give the outer surface of the core a ribbed appearance. The inner part of this core 

 is divided by transverse septas, arched slightly upwards, and connected with each other by a short, 

 thin, pointed, concentric axis, which usually projects from the centre of the terminating cell, in the 

 form of a prominent styloid process, which suggested to Lesueur the name of S/i//»ia. The increase 

 of the coral seems to take place partly by the springing up of young, small, prismatic cells between 

 the larger old prisms, and partly by the addition of new cells on the top of the old ones. 



" Fig. 6. Another species, or perhaps only a variety of this coral, occurs in the same part of the Carboni- 

 ferous Limestone of Iowa and Missouri, especially when the beds assume a dolomitic compo- 

 sition. The internal structure of this Lithostrotion is essentially the same; it occurs, however, 

 in hemispherical masses, of which the tubes forming the cells are almost conical, and tapering 

 towards their origin, where they almost lose their prismatic form ; from their origin the groups 

 of tubes radiate in curves from the centre towards the circumference of the hemispherical mass. 



* See luble (jii p. 92, t Silliman's .Tounial, -vol, xliii,. No. 1, ,)uly. 18i2, p. 14. 



