MIOCENE ECHINODERMATA. 213 



Determinative characters. — Test moderate, ovoid, tall, apex slightly excentric forward, no 

 anterior groove, nearly flat below. Ambulacra narrow, paired in shallow grooves, antero- 

 lateral much longer than the posterolateral; pairs small, slitlike. Interainbulacra broad, 

 covered with very small tubercles. Fascioles indistinct. Peristome near forward margin. 



Dimensions. — Length 42 millimeters; width 37 millimeters; height 35 millimeters. 



Description. — This species was figured by Kavenel in 1848, and described and figured by 

 McCrady in 1858. The test is of moderate size, ovoid, and tall. The apex is slightly excentric 

 forward. There is no anterior groove, a slight depression extending from the apex part way 

 to the margin. The lower surface is nearly flat. 



The ambulacra are narrow, the posterolateral pair bent outward toward the margin. The 

 anterolateral nearly straight. The paired ambulacra in shallow depressions, long, open below, 

 the posterolateral shorter than the anterolateral pair. 



The interambulacra are wide, the paired interambulacra slightly gibbous at their upper 

 ends. Portions of the peripetalous and lateral fascioles are rather indistinctly shown. 



The peristome is near the anterior margin with a well-developed labrum. The periproct 

 is not shown on the single specimen of this species studied. 



Locality.— -N 'ear Oakley Inlet, Waccamaw, S. C. 



Geologic horizon. — Miocene. 



Collection. — American Museum of Natural History. 



Genus ECHINOCARDITXM Gray. 



Echinocardium orthonotum Conrad. 



Plate XCVII, figs. 2a-c; Plate XCVIII, figs, la-c, 2a-c. 



Spatangus orthonotus Conrad, 1843, Acad. Nat. Sci. Philadelphia Proc, vol. 1, p. 327. 



Amphidetus virginianus Forbes, 1845, Geol. Soc. London Quart. Jour., vol. 1, pp. 425, 426, 3 figs. 



Amphidetus virginianus Forbes, 1846, Geol. Soc. London Proc, vol. 6, pp. 559, 560, 3 figs. 



Amphidetus orthonotus Tuorney and Holmes, 1S55, Pliocene fossils, South Carolina, pp. 6, 7, figs. 1, la-c. 



Amphidetus virginianus Emmons, 1858, North Carolina Geol. Survey Kept., p. 310, fig. 245a-c. 



Echinocardium virginianum Desor, 1858, Synopsis echinides fossiles, p. 408. 



Echinocardium orthonotus Conrad, 1865, Acad. Nat. Sci. Philadelphia Proc, vol. 17, p. 75. 



(?) Echinocardium pennatifidum A. Agassiz, 1872, Revision of the Echini, pt. 1, p. 111. 



Echinocardium orthonotum A. Agassiz, 1874, Revision of the Echini, pt. 4, p. 751. 



Amphidetus virginianus Schluter, 1899, Deutsche Geol. Gesell. Zeitschr., vol. 51, p. 113. 



Echinocardium orthonotum Clark, 1904, Maryland Geol. Survey, Miocene, pp. 430-432, PI. CXIX, figs. la-c. 



Echinocardium orthonotum Stefanini, 1911, Soc. geol. italiana Boll., vol. 30, p. 706. 



Determinative characters. — Test large, ovate to cordiform, elevated, upper surface nearly 

 flat forward, deep and broad, anterior groove higher posteriorly with truncated surface, tumid 

 plastron below. Ambulacra wide, anterior in broad groove, paired ambulacra in shallow 

 grooves triangular in outline, widely open above, narrow below; pore pairs large and not numer- 

 ous. Interambulacra narrow above, wide below; fascioles distinct. Peristome large, slitlike. 

 Periproct high on posterior truncation. 



Dimensions. — Specimen A: Length 58 millimeters; width 52 milhmeters; height 29 milli- 

 meters. Specimen B: Length 51 millimeters; width 46 millimeters; height 29 millimeters. 



Description. — This species was first described by Conrad in 1843, but not figured. Forbes, 

 in 1845, redescribed and figured the form under the name of Amphidetus virginianus. The 

 test is rather large, irregularly ovate to cordiform, elevated but more posteriorly than anteriorly. 

 The upper surface is mostly flat forward. A broad and rather deep anterior groove with slightly 

 gibbous edges indents the upper surface but narrows and shallows toward the margin. The 

 posterior portion is elevated into a broad ridge which continues nearly to the truncated posterior 

 margin. The lower surface is nearly flat except for the elevated plastron. 



The ambulacra are wide, the anterior being situated in the broad anterior groove. The 

 paired ambulacra are situated in shallow grooves on the upper surface. They are triangular 

 in outline, widely open above and narrow below, the anterolateral being wider above than the 



