170 PANAMIC DEEP SEA ECHINI. 



The uniform size of the plates of the bivium and the included odd inter- 

 ambulacrum is most characteristic when seen from the abactinal side of 

 the test (PI. 03, fig. J). 



Both the ambulacral and interambulacral plates of the upper part of 

 the test are crowded with small miliaries (PI. 03, figs. 1, 2), arranged, in 

 some of the wider lateral interambulacral plates, in horizontal rows more 

 or less parallel with the sutures. In the other species of the genus this 

 miliary tuberculation is far more distant. 



The posterior extremity is vertically truncated and its height is very 

 considerable in proportion to that of the test (PI. 03, fig. 2), while in II. fulva 1 

 the height of the obliquel}- truncated posterior extremity is small compared 

 to that of the test; the anal groove (PI. 03, fig. /). is also very slight com- 

 pared to the deep narrow cut of 77. fulva. 2 The anal system is slightly 

 pyriform ; its greatest diameter is horizontal (PI. 03, fig. 5); while in 

 H. fulva 3 the anal system is longitudinally elliptical. This difference in 

 outline may, however, be partly due to differences in age. The anal system 

 (PI. 03, fig. 5) is covered with large irregularly pentagonal plates becoming 

 smaller towards the central anal opening ; above it the plates are small ; 

 they all carry a few miliaries. 



The subanal fasciole (PI. 63, fig. 5) is intermediate in outline between 

 that of II. gracilis* which is elliptical, and that of H. fulva? which has a 

 very angular pentagonal outline. 



On the actinal side (PI. 55, fig. 9) this species is marked by the great 

 width of the bare posterior lateral ambulacra and the length of the actinal 

 plastron ; this as well as the outer edge of the bare lateral ambulacra are 

 flanked by large secondaries (PI. 64, fig. 1) with sunken scrobicular areas 

 (PI. 03, fig. 7) elongated towards the ambitus, the boss sloping in the oppo- 

 site direction. In II. fulva the tuberculation of the plastron and of the 



peripetalous fasciole, the existence of a rostrum surrounded by a fasciole — all these are characters 

 which do not exist in any of the species of Homolanipas thus far described. 



M. de Meijere, in his Memoir on the Echinoidea of the -.Siboga'' Expedition, follows Dr. Mor- 

 tensen in his criticisms regarding the execution and arrangement of a number of the "Challenger" 

 Echini plates. These criticisms come with little grace from an author who gives his readers such 

 caricatures of Echini as Figs. 303, 313, 310, 369, 370, 372, 37:'.. 384, 385, 459, 400, 489 to 491, and 

 whose figures of the same species are far more scattered, and for no apparent reason, than those he 

 condemns. 



1 "Challenger" Echinoidea, PI. XXIV, fig. 1. 



2 Id. PI. XXIV, fig. 2. 

 » Id. PI XXIV, fig 4. 



4 Revision of the Echini, PL XVII. fig. 10. 

 6 " Challenger " Echinoidea, PI. XXIV, fig. 4. 



