388 University of California Publications in Zoology. [ VOL - 6 



fewer and scattered irregularly over the whole surface. It 

 should be noted that the two marginal clumps of spines at the 

 level of the acetabulum occur as they do in G. fimbriata. 



The distribution of spines was worked out in living as well 

 as preserved material, that no error due to loss of spines by 

 deterioration or action of reagents might enter. The distribu- 

 tion found resembles that given by Lonnberg for G. urna, except 

 that he describes spines as present along the whole length of the 

 lateral margins of the body, and along the lateral folds. The 

 distribution as given by Spencer (1889, p. 140) for G. rugosa is 

 substantially that found in G. urna (var.?) : 



"They are distributed generally over the body surface, but are most 

 numerous along the side folds, and more especially at the anterior end r 

 both on the dorsal and ventral surfaces, and again at the posterior end, 

 beyond the region of the side folds. They are sparsely distributed over 

 the central part of the body, both dorsally and ventrally. ' ' 



Haswell's figures (see my plate 47, figure 80) show spines of 

 great size distributed over the whole of the surface of the animal. 

 Wagener's (1852) figures show the acetabular clumps, and a 

 distribution of the spines in the posterior region similar to that 

 described by Lonnberg and given above for G. fimbriata. 



The small spines, irregularly distributed, vary in size from 40/*, 

 to 60/n by 15/x to 25/x, and in shape from simple rounded spinules 

 to a blunt-tipped, swollen-based form. Broad, triangular, 

 sharply pointed forms also occur, but less frequently (pi. 37 r 

 fig. 32). These spinules are not borne on papillae; they rarely 

 contain more than three concentric layers. 



The spines proper, from the extremities of the body, are of 

 fairly constant shape and size. In the acetabular region (pi. 37, 

 figs. 28, 29) they are bluntly rounded at the tip, swollen in the 

 middle third of their length to nearly three times the diameter 

 of the tip, narrowing again at the bluntly rounded base. They 

 are about 130/x by 36/x in size. In the rosette region, the spines 

 are of the same general shape (pi. 37, figs. 30, 35), but are of 

 considerably greater size, ranging from 185/t by 45/x to 220/w. 

 by 55/ut. 



The spines are composed of concentric layers of uniform 

 thickness, and are hollow. In macerated specimens the layers. 



