^t-ARK.l GONIOPVGUS ZITTKLI. 53 



The intorambulacral areas arc a))<)ut one aiul one-half times as wide 

 as tlie anibuhicral. They have two rows of])riniary tubercles that are 

 somewhat hirger than those oftlic anibulacia (PI. xviii. Fig. Id). The 

 areolas are very large and are continent above and below. Throughout 

 the greater part of the column the two rows approach each other, but 

 toward the apical disk are widely separated from one another. The 

 smaller tubercles are disi)osed iu rows, with greater or less regularity, 

 on either side of the primary series. 



The mouth oi)ening 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. (PI. xviil, Fig. la). 



Related forms. — This form is apparently closely related to Coptosoma 

 Mortoni, but is more elevated and does not exhibit the granules l)etween 

 the pores. 



Locality and geological horizon. — This species is from the yellow 

 limestone of the middle marl bed (upper Cretaceous) of Timber creek, 

 New Jersey. 



Collection. — Philadelphia Academy of Natural Sciences. 



GONIOPYGUS Agassiz. 



GONIOPYGUS ZiTTELI Clark, 



Plate XVIII, Figs. 2 a^d. Plate xix, Figs. 1 a-e. 



Goniopygus ZUteli Clark, 1891. Johns Hokins l^niversity CMrcnlars, No. 87, p. 76. 



Determinative characters. — Test subconoidal, circular in circumfer- 

 ence; upper surface elevated ; base tlattened. Ambulacra broad, with 

 a double row of alternating tubercles, eighteen to twenty in each series ; 

 poriferous zones, with a double row t>f i)ores, multiplied at the peri- 

 stome. Interambulacra broader than the ambulacra, with a double 

 row of primary tubercles, ten to twelve in each row. Apical disk prom- 

 inent, compact. Mouth o])ening large, with shallow incisions. 



Dimensions. — Transverse diameter, 1^ inches; height, 1 inch. 



Description. — All the specimens of this species examined by the 

 writer have a distinctly subconical form that is highly characteristic. 

 The npper surface is very much elevated, while the lower is flat and 

 slightly depressed around the mouth edges (PI. xviir. Fig. 2a). 



The ambulacral areas are broad, increasing regularly in width from 

 the apical disk to the ambitus, beyond which they decrease toward the 

 mouth opening (PI. xix. Fig. Id). There is a double r(»v of eighteen to 

 twenty tubercles in each area, that' rapidly increase in size from the 

 apical disk downward. The pores are arranged in a double row on 

 ea^ch poriferous zone except in the vicinity of the mouth edges, where 

 they become suddenly increased in mimber (PI. xvni, Fig. - />). 



The interambulacral areas are about one and one-half times the width 

 of the ambulacral, and each contains a double row of large tubercles. 



