Weno and Pawpaw Formations 113 



Anterolateral ambulacra: Diverge from apical system at angle of 180 

 degrees, then turn forward, their middle parts making, if produced, an 

 angle of about 45 degrees with each other ; then turn laterally and cross 

 the ambitus at a point posterior to the anterior corner of the test. The 

 anterior pore zone has 18 to 20 small, circular, closely spaced pore pairs. 

 The posterior zone has about 27 pairs of slit-like pores, the anterior pore 

 being much shorter. 



Posterolateral ambulacra: Short, inflated centrally diverge at angle of 

 about 130 degrees from each other. Each zone has about 12 pore pairs, 

 those of the posterior zone being more elongate than those of the anterior 

 zone. In each zone the anterior pore is shorter than the posterior. 



Apical system: Four genital plates, their conspicuous thick-lipped per- 

 forations making the four corners of a square. Oculars small, perforated. 



Peristome: Ovoid, depressed, posterior lip straight, with an elevated 

 median carina behind it. 



Periproct: Ovoid, inferior margin extended downward; situated at top 

 of vertically excavated area in posterior truncated area. 



This species is most similar to E. bravoensis Bose, from which it differs 

 in many particulars. E. bravoensis in form resembles E. texanus (Roe- 

 mer) and is the inflated texanus-like species which is widespread in the 

 upper Washita and which has been so frequently mistaken for E. texanus. 

 We have examples of it from the Weno to the Grayson formations, and it 

 has been found in the Buda limestone (Whitney) . E. bravoensis is not so 

 tall as E. texanus and is not therefore so inflated as. that species ; yet it 

 is more rotund than E. wenoensis* and lacks the angular contour of this 

 species. E. wenoensis is more ovate in form and does not have the long 

 posterior narrowing of the test seen in many individuals of E. bravoensis. 

 It is abruptly narrowed posteriorly and has a truncate posterior end. 

 There is variation in the figured material of E. bravoensis in this regard, 

 and in the absence of a designated type individual it is impossible to say 

 which condition is typical for that species. Bose's plate XLI, figure 5, 

 shows an individual in which the posterior narrowing is slight and the 

 truncation is broad, as in E. texanus or E. mexicanus; in plate XLII, 

 figure 9, the narrowing is prolonged and the truncation narrow, as in 

 E. wenoensis. However, a constant and distinctive feature of E. weno- 

 ensis is that the posterior end of the test is not merely truncate but is 

 deeply excavated vertically, and in this excavation the periproct lies. In 

 E. bravoensis as figured, the apical system is subcentral or at least far- 

 ther forward than in E. wenoensis; the main limits of the antero-laterals 

 therefore diverge at a wider angle (about 80 degrees) in E. bravoensis; 



