Mr. T. Higgin on some Caribbean Sponges. 297 



mean time the Rev. H. H. Higgins had secured by means of 

 a diver several examples of the species at Puerto Cabello, on 

 the coast of Caracas, some of which he preserved in spirit, 

 while the rest were brought home in a dried state. The acqui- 

 sition of these specimens shows us the sponge growing under 

 different outward forms, and affords the opportunity of careful 

 examination of the species. 



Its peculiar feature, as its specific name denotes, is the 

 birotulate flesh-spicule hitherto only observed in Spongilla 

 and some of the hexactinellid sponges, viz. Hyalonema. Al- 

 though extremely minute, the form of this spicule is precisely 

 that of the large one familiar to us in Hyalonema^ from which 

 it only differs in size and in the number of rays forming the 

 umbrella-like heads. In his remarks (foe. cit^ Mr. Carter 

 observes that the minute flesh-spicule in H. abyssi (considered 

 by him to be the " embryonic form " of the large one with 

 bent sliaft) is a complete birotulate, " each dome-shaped or 

 umbrella-like head of which is composed of twelve spines 

 webbed together," exactly like that which is found in the 

 West-Indian littoral sponges, in which, however, it only 

 appears in the minute form, and in them, therefore, must be 

 considered to be a maturely developed spicule. 



In form H. birotulata is massive, lobate, with uniformly 

 even but roughly reticulated surface, extending laterally into 

 irregular lobes, or into long, procumbent, straggling, compressed 

 branches, which unite where they touch and cross each other, 

 or into numerous pyramidic erect prominences growing close 

 togetlier and united at the base, crumb-of-bread-like and of 

 dark brown-purple colour. The skeleton-structure is an areo- 

 lar multispicular network, the main lines of which extend 

 from the base towards the surface, or in the direction of the 

 long axis of the branch, gradually tending outwards and 

 ending abruptly in lengths free for some distance from sub- 

 sidiary fibre, and thus producing aculeate surface-prominences. 

 The dermal sarcode, which is strengthened with a quantity of 

 fine acuate spicules lying in it confusedly, has a dull glaze 

 when dry ; it is not pierced with numerous small pores, but 

 the openings in it are all rather large, making it difficult 

 to distinguish the incurrent from the excurrent orifices where 

 the latter are not larger than the others. In the growing 

 portions the dermal sarcode is supported on the projecting 

 ends of the skeleton-fibre ; but in the older parts the subdermal 

 cavities have lost their surface-covering of sarcode, and the 

 sponge thus becomes pitted or honeycombed in appearance. 

 Thin sarcode densely charged with the peculiar flesh-spicule 

 tympanizcs the interstices of the network, dividing the mass 



