SYSTEMATIC DESCRIPTIONS SPATANGINA. 61 



terior. Ambulacral areas petaloid, subcostulate, very open distally, and 

 yet contracted a little at the ends. The anterior ambulacrum III longer, 

 straighter, and narrower than the others; the anterior pair II and IV is 

 shorter than the posterior pair. Poriferous areas strongly developed, with 

 very unequal pores, the internal rounded, the external long, narrow, and 

 transverse. Near the ambitus the areas cease to be petaloid and the pores are 

 reduced, as in all species of Echinolampas, to single series ranged obliquely 

 and scarcely visible in the midst of the tubercles; the poriferous areas 

 then converge in nearly a straight line to the peristome, around which, 

 without being very numerous, the pores appear to draw together and in- 

 crease a little. Tubercles are strongly scrobiculate, homogeneous, and 

 disposed without order, everywhere very abundant. Peristome relatively 

 large, subpentagonal and angular [sunken, opening a little posterior to or] 

 in the middle of the lower face. Periproct small, subcircular, inframarginal, 

 a little removed from the posterior border. The apical disk is compact, 

 slightly developed, and prominent. The madreporite is very extended, 

 forming a large part of the apical disk. Four genital pores, very open; 

 the anterior pair nearer together than the posterior pair. Ocular plates 

 are angular, very small, in direct contact with the madreporic plate. 



This species is very abundant in Trinidad and St. Bartholomew. 

 Measurements are taken from a Trinidad specimen in the collections 

 of the U. S. National Museum (No. 115389). Height, 19 mm., length, 

 42 mm., width, 33 mm. 



A large and very beautiful series of specimens from Trinidad, col- 

 lected by J. A. Bullbrook, are fine for a study of variation and for 

 structure as well, as they are beautifully preserved. Some of these are 

 broad and flattened, strongly resembling ly coper sicus; others are high 

 and rounded, as is typical of the species. The material came in after 

 this manuscript was finished and too late to make use of it further 

 than by this brief note. 



A large collection of specimens of this species made by Vaughan in 

 St. Bartholomew, with other material, gives good opportunity for 

 seeing the range of variation in this species, which is considerable. 

 Some are wide and quite flat, others narrow, elongate, rounded, and 

 high; the apical disk is quite uniformly close to the center of the test 

 or a little posterior. 



Echinolampas ovumserpentis approaches nearest to ly coper sicus of 

 all the West Indian fossil species, but is distinguished from that by 

 a number of characters. In ovumserpentis the apical disk is central 

 or slightly posterior; the ambulacral petals are truncate and extend 

 nearer to the ambitus; the tuberculation is coarser, with tubercles 

 relatively farther apart. There are typically 3 tubercles in a line across 

 the interporiferous area of an ambulacral petal ; the periproct is very 

 small and farther from the posterior border; the peristome is more 

 angular and more deeply sunken. On the other hand, in ly coper sicus 

 the apical disk is anterior, not central ; the ambulacral petals are flaring 

 at the tips and do not extend so near to the ambitus; the tubercula- 

 tion is finer, with tubercles more crowded. There are typically 6 



