CYSTECHINUS LOVENI. 159 



shape of the plates of the apical system. In C. clypeatus A. Ag. 1 the poste- 

 rior genitals are characterized by their lateral elongation and, as in C. 

 Wyvillii, by the great size of the posterior lateral ocular plates (PI. 80, 

 figs. 5, 6), Fig. 234. 



The test when seen from the actinal or abactinal side (PI. 75, figs. 1, 2) is 

 somewhat more pointed than in C. Wyvillii, A. Ag. 2 Seen in profile (Pis. 76, 

 fi°\ 1 ; 77, fig. 3) the shorter anterior extremity, and the slight re-entering out- 

 line of the sides of the test are in marked contrast with the gibbous outline 

 of the test above the ambitus, the deep re-entering curve, and the extension 

 of the anterior extremity of the test of C Wyvillii. 3 The more conical and 

 gibbous outline of C. Wyvillii? as contrasted with C. Loveni (PI. 76, fig. $) is 

 well seen on comparing the two figures here quoted. The coronal plates 

 are proportionally higher in G. Wyvillii than in C. Loveni. In a specimen 

 of the former of 88 mm. in length there are eleven plates in the odd anterior 

 ambulacrum from the apex to the ambitus, while in the latter, in a specimen 

 of the same size there are thirteen plates in the odd anterior ambulacrum 

 and nine in the odd interambulacrum. The most prominent character 

 of the test is the greater number of the fine primary tubercles in C. Loveni 

 (PI. 77) as compared with the coarser and more distant primaries of C. 

 Wyvillii. 5 The miliaries are also finer and more crowded in C. Loveni 

 (PI. 77). 



The size of the actinal plastron of C. Loveni (Pis. 77, fig. 5; 78, fig. 3) 

 is large as compared with that of C. Wyvillii. The rudimentary phyllodes 

 occupy five or six of the actinal ambulacral plates in the anterior lateral 

 ambulacra, three or four in the posterior ambulacra, and four or five in the 

 odd anterior ambulacrum (Pis. 76 figs. 4, 5 ; 78, fig. 3). There is a marked 

 thickening of the actinal plates adjoining the actinostome (Pis. 76, fig. 5; 

 78, fig. 5), forming a, low ridge much as it occurs in Echinolampas (PI. 64, 

 fig. 5) and Conolampas (PI. 65, fig. 6). The labium is by far the largest of 

 the primary interambulacral pktes (Pis. 77, fig. / ; 78, fig. 3). The ambu- 

 lacral plates of the actinal side are comparatively bare ; towards the ambitus 

 they become like the interambulacral plates thickly covered with primary 

 tubercles (PI. 77, fig. 1). 



I have already, when speaking of Urechinns giganteus, alluded to the 

 bare spaces occasionally occurring on the coronal plates, which would seem 



1 " Challenger " Echinoidea, PI. XXXVb, fig. 10. * Id., PI. XXIX, fig. 4. 



2 Id.., PI. XXIX», fig. 2. 6 Id., PI. XXIX\ figs. 1-4. 



3 Id., PI. XXIX", fig. 3. 6 Id., PI. XXIX', fig. 2. 



