440 STKONGYLOCENTROTUS DEPRESSUS. 



Actinal cuts slight. Poriferous belt of uniform width. Actinal membrane 



thin, with few irregular circular plates, in continuation of the ambulacra! 

 system, carrying miliaries. 



The color of the dried test is light violet above, whitish below; spines dark 

 purplish-brown at the swollen part of the shaft, lighter colored at base and tip. 



v,, r„teramb Diameter Diameter Diameter No. of Length of Diam. 



TubS! Diameter. Height. Abact. Syet Ul Syal AnalSyet. Pore.. Spine, oTSpine. 



16. 52. 26.6 18. 20 - 5 3 - x 



14. 

 13. 



44.9 22.7 9. 16.2 4.9. 7. 



38. 17.8 7.5 14. 3.9 6. 



Australia. 



Strongylocentrotus depressus 



! Toxocidari* depressa A. Ac, 1863, Proc. A. X. S. Phila, 



\ Slrongylocentrotus depressus A. Ac;., 1872, Rev. Ech. I't. L, p. 162. 



The measurements and proportions are nearly the same as those of S. tu- 

 berculatus. The greater flattening of test, with narrower coronal plates and 

 correspondingly smaller tubercles, seem however, al first sight, to character- 

 ize in a marked manner the specimens of this species. 



The primary tubercles of the ambulacra! and interambulacra! regions are 

 nearly of the same size. Owing to great flattening of test, the poriferous 

 zone is frequently extremely broad, the inner and one outer pairs of pores 

 becoming disconnected in specimens with a depressed test. This char- 

 acter distinguishes some of the specimens named E. disjunctus by Martens. 

 The actinostome is apparently proportionally much larger than in S. tuber- 

 culatus, especially in the smaller specimens, but with increasing si/.e this 

 difference becomes less apparent. 



A larger series of specimens than are now to be found in the different 

 Museums may show that there have been too many species recognized in 

 this genus among the species inhabiting the Chinese. Japanese, and Austra- 

 lian Seas, and that, as in other species of the family of Echinomctradae, 

 we find great local differences, as among the specimens of the two most com- 

 mon species of Echinometra which have been described under so many specific 

 names. The want of material, however, prevents us from applying ex- 

 tensively to this most difficult genus the results which have reduced the 

 number of species so materially in other genera, as we should only increase 

 the existing confusion by attempting to consolidate species about which we 

 know so little thus far. 



