298 TOXOPNEUSTES VARIEGATUS. 



system is the same in the two genera. In old specimens of Boletia we find, 

 during* the growth of the poriferous zone, that new plates are frequently 

 added at any point of the poriferous zone, thus introducing an element of 

 irregularity in the trigeminal arrangement, giving a greater preponderance 

 to the apparent vertical arrangement of the pores which is not found in 

 Lytechinus, though in young Boletia maculata, and up to the largest size, 

 the mode of growth of the poriferous /.one is the same as in the typical 

 Lytechinus, and in this species of Boletia the general features of Lytechinus 

 arc retained ; unfortunately the buccal membrane of B. maculata is not 

 preserved in any of the specimens examined, and 1 am unable to show any 

 correlation between these characters. For the present it does not seem 

 advisable to maintain Lytechinus even as a subgenus of (Boletia) Toxop- 

 neustes, until we know something more of the Boletia maculata. 



Toxopneustes variegatus 



! Echinus variegatus (Lamk.) 1816. A. s. Vert 



! To i variegatus A. A<; \~s. 1872. Rev. Ech., Pt. I. 



PI. //. /. .:. 6 ; PL IV". f. 4, 6 ; PL VII f. 7- SO. 



The tubercles both of the ambulacral and interambulacral areas are 

 arranged in perfectly regular vertical rows, closely packed on lower surfaces 

 in interambulacral area, but one vertical row of large tubercles extending 



from ambitus to the apex, the one next to the poriferous zone gradually becom- 

 ing much smaller, while the others, according to the size of the specimens, 

 extend more or less towards the abactinal region, leaving a bare median 

 space on which the granulation of the plate is very fine and compact. The 

 secondaries are far apart and irregularly scattered round the primaries. In 

 the ambulacra] space the outer vertical rows alone extend to the abactinal 

 region, the others but a short way above ambitus, leaving a bare median 

 space as in the interambulacral space. The spines vary very much in 

 thickness and coloration. The variety with long, slender spines, with a 

 greenish coloration of test, has been called E. variegatus ; specimens with 

 a uniform yellowish or violet tint, having at same time generally blunter, 

 stouter, and shorter spines, have received the name of carolinus and atlan- 

 ticus. The actinal cuts are moderate ; the buccal membrane is completely 

 covered by large, very prominent plates, closely packed together. The 

 depression of the median interambulacral space near apex, so common in 

 Boletia rosea, leaving the ambulacra raised, is frequently found in this 

 species also. 



