1887.] NATURAL SCIENCES OF PHILADELPHIA. 245 



or more long spines near the middle. Rotules consisting of three 

 to six irregularly placed rays, recurved at their extremities. 

 (Ibid. d,d,d.) 



Birotulates of the shorter class abundant and compactly arranged 

 around the gemmule; shafts mostly smooth, though sometimes bear- 

 ing a single spine ; irregularly cylindrical but rapidly thickening to 

 support the rotules, which are large, umbonate, nearly flat, and 

 finely lacinulate at their margins; occasionally microspined. (Ibid, 

 e, e, e.) 



3Ieas. Skeleton spicules 0"0075 by 0'00075 inches. Length of 

 long birotulates 0'0021, of short birotulates 0'0012 inches. Diameter 

 of disk of latter 0*0009 inches. 



Hab. On submerged wood, etc. 



Log. Collected by A.' H. MacKay Esq. of Pictou, Nova Scotia, 

 from several lakes upon the water-shed of that region; and later, 

 from similar situations in Newfoundland. 



The close general agreement of the above description, (prepared 

 while the writer was under the conviction that the sponge was a 

 distinct sj)ecies) with that just given of the typical H. rycleri, except 

 as regards the robustness and spinous character of their skeleton 

 spiculse, (features that we have already seen to be extremely varia- 

 ble) will, I think, help to explain, perhaps to justify my present 

 act in reducing it to the position of a variety of the latter. That 

 there are obvious differences between them is unquestionable; that 

 these differences are specific, I do not noiu believe. 



This beautiful sponge was first discovered by Mr. A. H. MacKay 

 during the summer of 1884, when its novelty, as indicated by its 

 unusually robust, entirely spined skeleton spicules, was easily imag- 

 ined; but the absence of gemmules at that time, precluded the 

 determination of its generic relations, and it continued for a while 

 unnamed. During the last week in December of the same year, a 

 further search was rewarded by the finding of other "specimens 

 upon sticks pulled up through a break made in the ice," and among 

 these a few and but a few gemmules were discovered. These sufficed 

 to place it clearly within the genus Heteromeyenia, with the final 

 designation as indicated above. 



The skeleton spicules of this variety are more entirely and con- 

 spicuously spined than those of any other known North American 

 sponge. In some forms of Meyenia fluviatiUs they are noticeably 

 sj)iniferous, though the terminations are generally naked; in Tuhella 



