102 H. L. Hawkins—On Lovenia forbesi 
bordering upon ambulacra IJ and IV. This in itself may be regarded 
as a piece of confirmatory evidence for the association with an ambu- 
lacrum of the contiguous columns of the interambulacra, as urged by 
Jackson (Phylogeny). The crushing occurs, to some degree, in all 
four of the lateral interambulacra, and even in area 5 an appreciable 
reduction in the height of the plates can be detected. It affects most 
seriously those plates that are next above the enlarged subambital 
plates; and is most intense in specimen B, the older of the two. In 
o Its 
3 Sues 
TEXT-FIG. 1.—Plan of the adoral and part of the adapical surfaces of 
specimen A of Lovenia forbesi. x about 24. The lettering and 
numbering of,areas and plates,is in accordance with the method employed 
in Lovén’s Htudes sur les Echinoidées. The ambitus is approximately 
coincident with the outer margins of the plates numbered 2. All 
ornament is omitted. 
such specialized forms as Zovenia, these plates (Nos. 2 or 2+ 3), 
together with the primordial unpaired plate, become set apart early 
in ontogeny for the purpose of building a strong, flat adoral surface. 
There is practically no resorption cf plates at the peristome; and, 
indeed, one might even regard the great increase in size of the adorally 
situated plates as constituting a ‘‘ negative resorption ”’, and possibly 
exerting pressure upwards. 
