AMERICAN SPECIES OF OKTHOPHBAGMHSTA AND LEPIDOCYCLINA. 



63 



This is by far the largest species of the Coastal 

 Plain and is surpassed in size only by L. de- 

 pliantina Munier-Chalmas, of Europe, and L. 

 undulata Cushman, of Antigua. 



Lepidocyclina gigas Cushman. 



■ Plate XIX, figures 1-4. 



Lepidocyclina gigas Cushman, Carnegie Inst. Washington 

 Pub. 291, p. 64, pi. 1, figs. 3-5; pi. 5, fig. 4, 1919. 



Test large, flattened, somewhat lenticular, 

 circular in outline; central portion slightly um- 

 bonate; thence gradually thinning toward the 

 periphery, which is bluntly angular; surface 

 generally flat and smooth, occasionally slightly 

 undulating. 



The vertical section shows the equatorial 

 chambers increasing somewhat in height from 

 the central area toward the periphery, the per- 

 ipheral end of each chamber slightly convex 

 toward the exterior; lateral chambers broad 

 and low, in vertical columns, usually from 7 to 

 10 in each column in the central portion of the 

 test outside the umbo, thence gradually de- 

 creasing in number toward the periphery. 

 PiUars are developed at irregiilar intervals but 

 are few in number and of very small diameter. 



Horizontal sections (PI. XIX, fig. 4) show 

 the hexagonal equatorial chambers, the annu- 

 lar rows of which are very uneven in size, and 

 the subequal embryonic chambers. 



Diameter of largest specimens 80 millimeters 

 or more. 



The type locality for this species is U. S. G. S. 

 station 6862, Antigua, Leeward Islands, lower 

 bed at Hodges Bluff; T. W. Vaughan, col- 

 lector. Specimens from this locality are 

 numerous and very fine. Material that is 

 poorer but apparently specifically the same 

 occurs at stations 6854, Rifle Butts, and 

 6857, on the southwest side of Wetherell 

 Mill, both in Antigua. 



This species is very near to L. elephantina 

 Munier-Chalmas, but the two early chambers 

 do not seera to be at all alike, those of L. ele- 

 phantina being very dissimilar in size and 

 shape, whereas those of L. gigas so far as made 

 out seem to be much more nearly equal, as is 

 usual in American species of Lepidocyclina. 

 Plate XIX, figure 4, shows the two early cham- 

 bers of this species. 



This is a very fine and large species and 

 seems to be abundant at the type station. 



Lepidocyclina gigas Cushman var. mexicana Cushman, 

 n. var. 



Plate XIX, figui-e 5; Plate XX, figures 1, 2; Plate XXI, 

 figures 1-3. 



Test differing from the typical L. gigas in the 

 somewhat smaller size and the comparatively 

 greater thickness at the umbo; the surface is 

 apparently more reticulate, but this may be 

 due to the difl^erent conditions of preservation 

 in the two areas. 



Diameter of the test as much as 50 millimeters 

 or more; thickness in the umbonal region, 7 

 millimeters. 



The vertical section (PL XIX, fig. 5) is 

 very similar to that of L. gigas, but has a 

 rather less number of lateral chambers, and the 

 whole test except the umbonal region is some- 

 what thinner. 



Type specimen and others from Mexico col- 

 lected by E. T. Dumble. The type, from the 

 Meson formation. Meson, Vera Cruz, Mexico, is 

 referred to by Dumble ^ under the name "Orli- 

 toides papyracea." Large specimens that seem 

 very similar occur in the material collected by 

 Dumble from the San Rafael formation at 

 Cerro Cortado, Topila Hills, 15 miles south- 

 west of Tampico. Some of the Topila HiUs 

 material contains other species, but they are 

 not sufficiently weU preserved for positive de- 

 termination at present. 



Lepidocyclina fragilis Cushman, n. sp. 



Plate XXII, figures 1, 2. 



Test of medium size, 10 to 12 millimeters in 

 diameter, very thin, flattened or very slightly 

 seUaeform; central portion very slightly thick- 

 ened but usually forming no definite ■umbo 

 distinguishable from the remainder of the 

 test; surface very smooth except where eroded 

 and at the periphery, where the waUs of the 

 equatorial chambers form a slight reticulation 

 of the surface; whole test thin and fragile; 

 thickness usually about 1 milhmeter or less. 



The horizontal section shows the equatorial 

 chambers to be hexagonal and with fahly thick 

 walls. Embryonic chambers not seen. 



The vertical section shows the equatorial 

 band of chambers unusually low throughout, 

 increasing very little from center to periphery; 

 the chambers toward the center thin-walled 



1 Durable, E. T., California Acad. Sci. Proc, 4th ser., vol. 8, p. 

 147, 1918. 



