42 PROF. F. J. BELL ON ECHINANTHUS TUMIDUS. [Jan, 15, 



disposition of these odd pores to call to mind the characters of an 

 Echinolampas. 



The madreporite occupies the centre of the apical area, and the 

 five genital pores are quite distinct ; the two smallest are those that 

 lie to the left, and the anterior one on the right is a little smaller 

 than the other two ; between these last lies an ocular pore almost as 

 large as they ; all the other ocular pores are quite small. 



The sutures between the coronal plates are, on the abactinal surface, 

 remarkably distinct ; the tubercles are all of moderate size, subequal, 

 and minutely perforated at their tip ; they are not closely packed, 

 and the intervals between them are occupied by miliaries rather 

 coarser than those of E. testudinarius. 



The tubercles on the actinal surface are a little larger and rather 

 more closely packed ; they are more deeply sunken, and the miliaries 

 are rather coarse. 



Mouth deeply sunken. Owing to its injured condition it is 

 impossible to say how much or how little has been removed, and I 

 cannot follow Mr. Tenison- Woods in giving an exact statement as 

 to its size or shape. 



The pillars within seem, so far as one can judge by the touch, to 

 be well developed, and are to be felt just within the margin of the 

 injured mouth ; so that they extend over at least three fourths of 

 the radius of the internal cavity. 



During life the test would seem to have been covered with primary 

 and secondary spines, both of which were short, and the former 

 about twice as stout as the latter ; they were coarsely striated, had 

 a strongish ring, and were probably of a yellowish-green colour. 



The dried test is brown, but the colour is not uniform, being darker 

 at the ambitus than in the enclosed region ; the colour below more 

 uniformly brownish. 



Length 140, breadth 116, longest axis of anus 8 mm. 



Hah. . Mr. Tenison-Woods states that he has " every 



reason to think (it) came from the coast of N. S. Wales, though 

 there is no precise information as to its habitat." The injuries 

 received by the specimen indicate that it was speared by the pronged 

 instruments with which flat fish are fished for in Port Jackson and 

 its neighbourhood. 



Theoretical Considerations. — It will be clear enough that the 

 generic definition of Echinantlms will have to be very considerably 

 altered, if we allow the species now described to remain within its 

 limits. 



Hardly any character is of greater importance among the Echi- 

 noidea in general than that of the disposition of the pores in the 

 ambulacral plates ; among the Petalosticha this character rises to be 

 one of supreme importance, and is, I believe, the best criterion of 

 the extent and intimacy of generic relations. 



In forms already known to us we find that the pores may be set in 

 straight parallel rows which, at the region of the ambitus, become 

 more or less irregular and scattered, e. g, Palceolampas crassa ; or the 

 pores of one half may be less numerous than those of the other, e, g. 



