586 Yerrill, Notes on Radiata. 



line and general appearance, and in all the mai'gin is thick, with the 

 five large notches widely open, though in the larger there appears to 

 be a tendency to close the anterior pair. The posterior inter- 

 amhulacral opening is large and hroad-oval with thickened borders in 

 all, but there is a variation of more than 50 per cent, in its relative 

 size ; the region around it is in all more elevated than the central 

 reo-ion and considerably swollen. The form of the ambixlacral rosette 

 varies considerably. The three anterior petals are subequal and 

 usually long-oval, obtusely rounded at the end, but in one case they 

 are narrower and more elliptical, especially the odd anterior one, 

 which is widest in the middle, tapering to each end, and in another 

 they are broader and more dilated outwardly than usual ; the two 

 posterior ones are much longer, widest outwardly, and cui-ve some- 

 what aroimd the posterior opening, but they vary considerably in 

 relative width. The following are the proportions in two extreme 

 specimens : 



From abactinal center to posterior edge, -- 2 



Center to anterior edge, -- 1 



Center to lateral edge, 2 



Length of anterior odd ambnlacral petal, from center, 1 



Greatest breadth of do., - 



Breadth of its enclosed area, 



Length of anterior-lateral pair, -.- 1 



Breadth of do.,. 



Breadth of enclosed area, --- - 



Length of posterior pair - 1 



Breadth of do., - 



Breadth of enclosed area, - 



The branchings of the ambulacral grooves beneath are quite con- 

 stant in their arrangement, but the relative breadth and form of the 

 enclosed areas are quite as variable as in the dorsal rosette. The re- 

 gion about the anal opening and around the posterior foramen is 

 sometimes deeply concave \)r excavated; but in most cases slightly, 

 and sometimes not at all so. 



Encope Californica Verriii. 



American Jour. Science, xlix, p. 97, 1870. 



Plate X, figures 5 and 6. 



Test broad, thin at the edge, rounded anteriorly, broadest behind 

 the middle, sub-truncate or rounded posteriorly ; usually about as 

 broad as long, sometimes broader than long. Apex behind the cen- 

 ter. In profile the outline descends from the center to the anterior 



