274 Mr. H. J. Carter on two undescribed Sponges 



which closely resembles that of the Esperiada3, together with 

 the absence of horny fibre, a minimum of sarcode, and predo- 

 minance of spicules, including tricurvate and anchorate ones, 

 altogether claim for it a place in Dr. Gray's second subsection 

 of Spicular Sponges, viz, his '' Sisiculospongi^e ;" for here, 

 contrary to the character of Ectijon sjkivsus^ we have the 

 spicular element developed at the expense of the sarcodal one, 

 that is, an increase in the number of spicules and a reduction 

 of the kerataceous fibre to a delicate sarcodal film. 



The term " Halichondria^ " for this section of sponges is 

 not near so expressive or intelligible, and therefore not near 

 so well-chosen, as that of " Spiculospongia3." 



Thus Acarnus intiominatus would come into Dr. Gray's 

 second family, viz. " Esperiadte ;" and here I should be in- 

 clined to place it next to the genus Microciona^ p. 535 {I. c), 

 whereabouts it would probably have been placed by Dr. Gray 

 himself, instead of among his Tethyadie, had Dr. Bowerbank's 

 figure been more detailed. 



The anchorate spicule is precisely like that of Microciona 

 atrosanguineay Bk. ; but the bow-like or tricurvate one is 

 stouter and more arched. Again, the larger spicules of both 

 are acuate ; and although there is no isodictyal structure in M. 

 atrosanguinea^ from its peculiar mode of growth, the bulbous 

 ends of many spicules of the latter, which are also globular, 

 are sunk into the sarcode precisely in the same manner as the 

 fixed ends of the capitate spicules in Acarnus innominafus. 

 There are also in both species a few long spicules of hair-like 

 fineness ; but whether they are the earlier stages of the larger 

 ones, or permanent forms, I have not been able to determine. 



Microci07ia atrosanguinea^ which is also one of the com- 

 monest sponges on this coast, is set down by Schmidt, in his 

 ' Synonymy of Dr. Bowerbank's Sponges,' as a " Desmaci- 

 dine," and hence would come under his family " Desmaci- 

 dinffi," which, according to his "Sponge Pedigree" (Atlant. 

 Spong. Faun. p. 83), are among the latest developments of 

 his Protospongiae, while the Ventriculitidje are among the 

 most ancient. Now the bihamate spicule is as characteristic 

 of Schmidt's Desmacidinte as the little siliceous ball is of his 

 Geodinida? ; and both of these abound together fossilized in the 

 " Upper Greensand " of Haldon Hill, in Devonshire (Annals, 

 Feb. 1871, p. 112 &c.), while the Ventriculites as yet appear 

 to have been found only in the Chalk, which is a subsequent 

 formation. How this discrepancy, which makes the Ventri- 

 culitid^ the ancestors of the Desmacidinffi and Geodinida, is 

 to 1)6 reconciled is left for the evolutionist to explain. 



I have stated that the acuate spicules form the lines of the 



