

BRISSOPSIS. 199 



Peripetalous fasciole in some places double, triple or even multiple Plethotaenia. 



Petals flush, often not distinctly petaloid. 



Paired ambulacra not petaloid or if so, widely open at end and not 

 abruptly limited by peripetalous fasciole. 

 Test rather high, v. d. .40-.50 length, highest at apical system Linopneitstes. 



Test more flattened, v. d. .30-40 length, highest back of apical 



system Elipneustes. 



Petals short well formed with definite interporiferous areas and termi- 

 nated by the peripetalous fasciole. 



Posterior petals as wide near their rounded tips as at middle; am- 

 bulacrum III not depressed and anterior ambitus evenly convex . Eupatagus. 

 Posterior petals much narrower near their bluntly pointed tips 

 than near middle; ambulacrum III more or less depressed, at 



least at ambitus Gymnopatagus. 



No peripetalous fasciole. 



Sternum more or less well developed, much longer than wide, fully covered 

 with tubercles, the tuberculated portion extending more than half-way 

 from subanal plastron to peristome. 



At least ten distal pore-pairs developed in anterior series of petals II 



and IV; genital pores 4; labrum short and wide Spatangus. 



Only 4-8 distal pore-pairs developed in anterior series of petals II and 



IV; genital pores 3; labrum long and narrow Gonimaretia. 



Sternum small, wide, the tubercles confined to the posterior end or at least 

 not extending half-way from subanal plastron to peristome; labrum very 

 long and narrow. 



Periproct nearly or quite flush with posterior end of test; genital 



pores 4 Maretia. 



Periproct deeply sunken and overhung by posterior end of test; genital 



pores 3 Pseudomaretia. 



An internal fasciole present. 



Peripetalous fasciole present Breynia. 



No peripetalous fasciole present. 



Large, deeply sunken primary tubercles present in interambulacra on both 

 upper and lower surfaces; labrum very long and narrow; sternum with 

 tubercles confined to posterior part. 



Petals I and V well formed Lovenia. 



Petals I and V not at all petaloid Pseudolovenia. 



No large deeply sunken primary tubercles; labrum short and wide; sternum 

 well covered with tubercles Echinocardium. 



Brissopsis. 



Agassiz, 1840. Cat. Syst. Ect., p. 5 (nomen nudum). 

 Agassiz and Desor, 1847. Ann. Sci. Nat. Zool., (3), 8, p. 14. 



Type, Brissus lyrifer Forbes, 1841. British Starfishes, p. 187. 



Not only is this one of the most wide spread of spatangoid genera, but it is 

 one of the most perplexing from a taxonomic point of view. The species are 



