Classification of the Spongida. 141 



lated dermal layer, that gives the surface a smooth or even 

 uniform aspect. Vents well marked, scattered*. Spicules 

 chiefly of one kind, viz. simple acerate, more or less finely 

 pointed, and confined to the interior of the fibre. Texture 

 fine, compact, or coarse and open, varying with the size of 

 both spicule and fibre. Forms vertical, branched dichoto- 

 mously or polytomously, stipitate ; branches digitiform, cy- 

 lindrical, solid, terminating in rounded extremities, separate, 

 or united laterally and interruptedly (i. e. fenestrately ) , or 

 united laterally and generally throughout (i. e. flabellately), 

 lobed or proliferous. 



Group 2. Palmata. 



The same as the foregoing, but with flattened massive 

 digitations and large scattered vents. 



Group 3. Reptata. 



The same as the foregoing, but procumbent, more or less 

 sessile throughout or at intervals, with large crateriform or 

 well-marked vents. 



Group 4. Spinifera. 



The same as the foregoing, but with the branches more 

 cylindrical, defined, and prickly or aculeate. 



Family 2. Cavochalinida. 



Group 5. Tubulodigitata. 



Similar to " Digitata " and " Reptata," but with the digi- 

 tations tubulate. (When the vents are prolonged upwards 

 from a reptant solid branch, they become tubular digitations.) 



Group 6. Aculeata. 



Sarcode pale tawny or grey when dry. Skeleton the same 

 as the foregoing. Fibre the same, but growing out from the 

 external surface into more or less prominent aculeations or 

 conical eminences like prickles, sometimes an inch high, linked 

 together here and there by angular ridges which, radiating 

 from their sides, tend to an irregularly polygonal division of 

 the otherwise smooth surface ; divisions more or less cup-like, 



* " Pores." As these are too small to be seen by the unassisted eye 

 (being generally about a 1000th of an inch in diameter), and always 

 situated in the sarcode tympanizing the interstices of the dermal reticu- 

 lation, while their smallness for the most part renders them of no specific 

 value, they will be seldom mentioned. 



