62 MESOZOIC AND CENOZOIC ECHINODERMATA OF THE UNITED STATES. 



each, that gradually diminish in size toward the poles ; poriferous zones sinuous ; pores uuiserial. 

 Interambulacra with two rows of tubercles slightly larger than those of the ambulacra. Peri- 

 stome one-third the diameter of the test. 



Dimensions. — Diameter 17 millimeters; height 9.5 millimeters. 



Description. — This delicate species has a circular test with inflated sides. Both poles are 

 flattened, the lower more than the upper. 



The ambulacra are wide and prominent, and bear two rows of large tubercles, twelve or 

 thirteen in each row. The areolas are nearly confluent above, and below and are striated by 

 irregular radiating ridges. The bosses are deeply crenulated, and the small mamelons are imper- 

 forate. Minute tubercles and granules irregularly surround the primary tubercles, occurring 

 in greatest number along the central suture. The poriferous zones are slightly sinuous, the 

 three pore pairs having a curved arrangement on each ambulacral plate. 



The interambulacra are about one and one-half times as wide as the ambulacra. They 

 have two rows of primary tubercles that are somewhat larger than those of the ambulacra. The 

 areolas are very large and are confluent above and below. Throughout the greater part of the 

 column the two rows approach each other, but toward the apical system they are widely sepa- 

 rated from one another. The smaller tubercles are disposed in rows, with greater or less regu- 

 larity, on either side of the primary series. 



The peristome is narrow, occupying a little more than one-third of the diameter of the test. 

 It has an irregular pentagonal outline. The discal opening is large and pentagonal in form. 



Related forms. — This form is apparently closely related to C. mortoni, but is more elevated 

 and does not exhibit granules between the pores. 



Locality. — Timber Creek, N. J. 



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



Collection. — Academy of Natural Sciences of Philadelphia (146S). 



Coptosoma mortoni (De Loriol) . 



Plate XXII, figures la-e. 



Cyphosoma mortoni De Loriol, 1887, Recueil zool. Suisse, vol. 4, No. 3, pp. 389-391, PI. XVII, figs. 2a-c. 

 Coptosoma mortoni Clark, 1893, Johns Hopkins Univ. Circ, vol. 12, No. 103, pp. 51, 52, PI. XVII,. figs. la-e. 



Determinative characters. — Test circular, depressed. Ambulacra very wide, with two rows 

 of primary tubercles, thirteen in each row, the three or four at the ambitus large and nearly con- 

 fluent, but diminishing rapidly in size toward either pole; poriferous zones narrow, sinuous; 

 pores uniserial, those of each pair separated by a granule. Interambulacra with two rows of 

 tubercles, nine or ten in each row. Peristome very large. 



Dimensions. — Diameter 12-15 millimeters; height about 6 millimeters. 



Description. — The writer has been unable to obtain a specimen of this species, but the very 

 full description and excellent figures given by De Loriol admit of its satisfactory identification. 

 The description that follows is largely a translation of that given by De Loriol. The two speci- 

 mens in the possession of De Loriol were so deformed that he could not determine the height 

 accurately. The test is circular and depressed. The ambulacra are relatively very wide, 

 almost as large as the interambulacra, and bear two rows of large tubercles, thirteen in each row. 

 The first four or five tubercles from the apical system are far apart and very small. At the 

 ambitus three or four of the tubercles are very large, with nearly confluent areolas, but rapidly 

 diminish in size toward the lower surface, the last four or five being very small and with diffi- 

 culty distinguished. The areolas, except at the ambitus, are not large. The bosses are finely 

 crenulated and the mamelons small and imperforate. Upon the lower surface there are large 

 mammillated granules which can be with difficulty distinguished from the primary tubercles. 

 Each areola is also partially surrounded by a circle of small granules that occur most numer- 

 ously near the line of the central suture. The granules are few in number on the upper surface. 

 The poriferous zones are narrow, slightly sinuous, and composed of small pores without any 

 increase between the apical system or peristome. A small granule is found between the pores 

 of each pair. 



