ECHINOMETKA OBLONGA. 433 



creases near the abactinal system and near the month (from seven to three 

 and two). Supposing the long axis to be the longitudinal axis of the test, 

 the madreporie genital will become the hindmost right genital plate. The 

 anal plates cover comparatively only a small space. The longest spines are 

 about three fourths of the transverse diameter of the test. Their color is 

 purple, which also is the color of the test. Height, 32 mm - ; breadth, CG mm - ; 

 length, 70 mm -, longest spines, 57 mm \ The transverse diameter of the actino- 

 stome is 28 mm - and 27 mm '. 



The locality from which Dr. Liitken's specimen came is not known. A 

 specimen in the Jardin des Plantes is said to come from the West Coast of 

 Africa. Dr. Lutken thinks it more probable that New Guinea is the home 

 of this species. This is an interesting species, representing as it does the 

 petaloid actinal ambulacra of Echinometra ; and on same grounds which in- 

 clined Dr. Lutken and myself to separate the petaloid Strongylocentrotus 

 from the typical genus as a separate genus (Toxocidaris and Anthocidaris), 

 Dr. Liitken separated Ellipsechinus from Echinometra. I think, from what 

 I have shown of the development of Strongylocentrotus and Echinometra, 

 that such a distinction of the structure of the actinal part of the ambulacra, 

 though it may serve as a very convenient specific key for discriminating 

 groups of species, has no generic value, as is also hinted at by Dr. Lutken 

 himself in the remarks subsequent to his description of this species. 



Echinometra oblonga 



! Echinus oblongus Bl., 1825, Diet. Sc. Xat. O. 



'.Echinometra oblonrja Blainv., 1834, Actin. \_L I. AAA I I.J. 5. 



This species has not received the recognition to which it is entitled from 

 its marked characters. Covered with the spines it is at once recognized by 

 the short spines, their great, thickness, frequentky swollen in the centre of the 

 shaft; and when denuded, by the great size of the two primary vertical rows 

 of tubercles in the interambulacral spaces. The secondary tubercles remain 

 small above the ambitus, and in the ambulacra are reduced to small granules. 

 The poriferous zone is narrow ; the arcs of pores nearly vertical, spreading 

 but slightly; pores are large, not more than five in an arc. The general out- 

 line of test is elongate, elliptical, highly arched, with a thick test, The abac- 

 tinal system is compact; the anal system comparatively large; the madreporie 

 body greatly exceeding in size the other genital plates. The actinal system 

 is nearly elliptical, with actinal cuts barely marked. The anal plates, as well 



