1880.] 



PROF. F. J. BKLL ON THE TEMNOPLEURID^. 



439 



For the purpose of this investigation it is unnecessary to enter into 

 a detailed comparison of the two admirable sets of figures of A. 

 formosus and A. pallidus given by Valenciennes in the jilates to the 

 ' Voyage de la ' Venus,' ' ' for there is no question as to the existence 

 of two very different forms ; the difficulty lies rather in the presence 

 of intermediate forms. Thus both Valenciennes and Agassiz would 

 seem to look upon the rarer sutural pores of A. pallidus as an 

 important distinction ; but specimens, and those always small, will 

 be found in which these pores are just as numerous as in A. formosus ; 

 and, on the other hand, there may be found examples of A. formosus 

 in which the sutural pores are just as rare as in the typical A. pallidus. 

 Again, although they are rare, secondaries and miliaries are to be 

 found in the poriferous zones of A. formosus, and may be rare enough 

 in A. pallidus. 



I am, on the whole, inclined to keep these two species distinct; 

 the differences in proportion are differences which, if, on further 

 investigation, the results here attained to shall be confirmed, should 

 of themselves be regarded as at least of equal value with such emi- 

 nently variable characters as the number of pores or the distribution 

 of miliary tubercles. But, while I thus exhibit a somewhat stronger 

 inclination than Prof. Agassiz to keep the species separate, I shall, 

 no less than he, look out anxiously for those intermediate forms, of 

 which he speaks with such confidence. 



VI. HOLOPNEUSTES. 

 HOLOPNEUSTES POROSISSIMUS. 



The single specimen by which this genus or subgenus is repre- 

 sented in the Museum belongs, I fancy, to this species, and not to 

 H. purpurascens, as stated by Prof. Agassiz. I give the more 

 impertant measurements, which throw into relief the rather small 

 size of the actmal and abactinal areas, and the extraordinary develop- 

 ment of the poriferous zone. 



Percentage value of 



Diameter. 

 millims. Height. 

 52 78-8 



Abactinal 

 area. 

 15-3 



Anal area, 

 6-9 



Actiuostome. 

 22-1 



Poriferous 

 zone. 

 6-2 



Zoophytes, pi. ii. 



