CRETACEOUS ECHINODERMATA. 99 



Genus LINTHIA Merian. 



LlNTHIA TUMIDULA Clark. 



Plate LIII, figures la-i. 



Lintkia tumidula Clark, 1891, Johns Hopkins Univ. Circ, vol. 10, No. 87, p. 77. 

 Linthia tumidula Clark, 1893, Johns Hopkins Univ. Circ, vol. 12, No. 103, p. 52. 

 Linthia tumidula Clark, 1893, U. S. Geol. Survey Bull. 97, pp. 91, 92, PI. I, figs. la-i. 



Linthia tumidula Weller, 1907, Cretaceous paleontology of New Jersey: Geol. Survey New Jersev, pp. 304-305, PI. 

 XVIII, figs. 1-9. 



Determinative characters. — Test oval, cordiform, elevated; apex central; posterior border 

 obliquely truncated, anterior portion grooved by narrow sulcus; sides sloping. Ambulacral 

 furrows long, straight, depressed; poriferous zones broad, pores oval. Apical system small, 

 nearly central. Periproct on truncated posterior border. Peripetalous and lateral fascicles 

 distinct. 



Dimensions. — Length 53 millimeters; width 50 millimeters; height 28 millimeters. 



Description. — This large form has an elevated test, with flattened, sloping sides, oval outline, 

 and a narrow, moderately depressed, anterior sulcus that grooves the anterior margin. The base 

 is flat, except for the peristomial depression. 



The ambulacra are narrow and furrow for a long distance the upper surface of the test to a 

 moderate depth. The poriferous zones are broad and straight. The pores are large and oval, 

 and those of each pair connected by a shallow furrow. The anterolateral petals reach far down 

 the sloping sides and are about one and one-half times as long as the posterolateral pair. 



The surface of the test is covered with minute, perforated tubercles that are much longer on 

 the base than on the upper surface. A microscopic granulation fills the space between the tuber- 

 cles. Both the peripetalous and lateral fascioles can be readily traced. The apical system is 

 small, nearly central, and slightly depressed. The peristome is transversely oval and situated 

 near the anterior margin. The periproct is small, oval, and situated but a short distance above 

 the posterior margin. 



Localities. — Timber Creek and Vincentown, N. J. 



Geologic horizon. — Vincentown sand of Rancocas group, Upper Cretaceous. 



Collections. — American Museum of Natural History, New York; Boston Society of Natural 

 History; Johns Hopkins University. 



Linthia variabilis Slocum. 



Plate LI V, figures la-1. 

 Linthia variabilis Slocum, 1909, Field Mus. Nat. Hist. Pub. 134, Geol. ser., vol. 4, No. 1, pp. 12-14, PI. Ill, figs. 1-11. 



Determinative characters. — Test cordate, upper surface elevated, under surface nearly flat, 

 sides inflated, apex nearly central. Ambulacra in relatively deep depressions. Peristome near 

 anterior margin. Periproct near top of posterior truncation. 



Dimensions. — Length 17. 1 to 31.6 millimeters; width 1G.6 to 29.1 millimeters; height 10.1 

 to 19.6 millimeters. 



Description. — Slocum says: 



Test distinctly cordate, truncated posteriorly, ventral surface depressed convex, dorsal surface elevated, forming 

 a sharp ridge in the posterior interambulacral area. Sides inflated and sloping to the lateral and anterior margins; 

 posterior truncation slightly concave and the angle between the truncation and the base line varying from 77° to 90°. 

 Ambulacral areas straight, petaloid, situated in conrparatively deep depressions of the dorsal surface. Anterolateral 

 pair about one and one-half times the length of the posterolateral pair, poriferous zones of these four petals wide, pores 

 elongated and slitlike. Each pair of pores connected by a shallow groove and the pore near the border of the 

 petal the larger. Unpaired anterior ambulacral area situated in a deep depression the continuance of which forms a 

 sulcus in the anterior margin. Poriferous zones of this area narrow and situated far apart. Pores round and each pair 

 separated by a tubercle. Interambulacral areas broad and composed of large plates. Surface of the test covered with 



