64 MACKOPXEUSTES SPATA.NGOIDES. 



* Macropneustes spatangoid.es A. Ag. 



Spatangus purpureus A. Ag. (non Leske nee auct.). Bull. M. C. Z., VIII., No. 2, p. 83, 1880. 

 Lesser Antilles. 82-373 fathoms. 



PL XXVII. 



The fragments of the Spatangoid which I referred in the Preliminary Re- 

 port to Spatangus purpureus, I find on closer examination to helong to the 

 genus Macropneustes. Although no complete living specimen was dredged, 

 yet a sufficient number of dead broken tests were collected to enable me to 

 restore this species satisfactorily, with the exception of the part near the 

 anal system. In general appearance and outline, as seen from above, this 

 species resembles Spatangus purpureus ; but it can at once be distinguished 

 by the high anterior part of the test, which in the abactinal part of tbe odd 

 ambulacrum rises above the apical system. 



The anterior ambulacrum is deeply sunken at the ambitus, in a groove 

 similar to that of Linopneustes longispinus. In old specimens the abactinal 

 part of the ambulacral petals are disconnected, much as in Echinocardium, 

 within the internal fasciole. On the actinal surface the tuberculation is quite 

 uniform in specimens of very different sizes. The larger primary tubercles 

 are found on the anterior part of tbe test, and in the posterior interambula- 

 cral area they diminish gradually in size towards the posterior extremity, 

 and become more closely crowded. The tubercles of the actinal plastron 

 are smaller and of uniform size. On the abactinal surface the primary 

 tubercles are limited to the interambulacral areas within the peripetalous 

 fasciole, except along the line of the middle of the posterior interambu- 

 lacral area, along which the V-shaped angular lines of primary and sec- 

 ondary tubercles extend, gradually diminishing in size towards the anal 

 system. Within the peripetalous fasciole the arrangement of the primaries 

 varies greatly. In some specimens there are not more than nine or ten 

 large tubercles in the apical part of the interambulacral areas; in others 

 the primary tubercles form V-shaped figures in each plate, tin 1 smaller tuber- 

 cles ou the lower side of the plates. In other specimens, again, the large 

 tubercles form merely irregular horizontal lines. The rest of the surface 

 of the test within the petaloid area to the actinal side is closely packed with 

 small miliary tubercles, often concentrated more or less on the lower part 

 of the coronal plates so as to form V-shaped areas. The petaloid ambulacra 



