406 Mr. II. J. Carter on Dee2)-sea 



ment. It differs from T. cranium in the following particulars, 

 viz. : — the anchoving-spicule of both forms (tiuke and fork) 

 are much larger and stouter ; in the fluked form (iig. 48, c) 

 the arms are much more expanded and not so recurved as in 

 T. cranium, while those of the forked form(fig. 48, a) are trun- 

 cated towards their extremities, which respectively terminate in 

 a cup-sha])cd excavation bordered by a serrated margin, while 

 the central canal at tlie bottom of the cup-shaped cavity divides 

 into a lash of branches, each of which goes to one of the tooth- 

 like processes on the margin of the cup (fig. 48, h). Neither 

 does the specimen, although in other respects exactly like 

 T. cranium, contain any flesh-spicules (bihamates). 



I have given the specimen a special designation ; but I am 

 very desirous not to introduce any thing into the description 

 of a sponge which even borders upon an abnormal or patho- 

 logical development of any part of it, as its natural varieties 

 are quite sufficient to occupy our attention at one time. If 

 their patliological ones are to be described, this should be done 

 separately, and in an article exclusively devoted to the subject, 

 as mixing the two must lead to inextricable confusion. 



Pachastrella amygdaloideSj n. sp. (PI. XIV. fig. 22.) 



General form almond-shaped, truncated at the apex, sessile. 

 Colour yellowish white. Surface even, rough ; structure of 

 dermal sarcode confusedly spiculous in direct continuation Avith 

 the interior, not corticate, charged with small, linear flesh- 

 spicules filling up the interstices of the larger radiate or ske- 

 leton ones. Pores in the interstices among the small linear 

 spicules, which are confusedly heaped together around them. 

 Vents congregated in a circular depression at the truncated 

 end (fig. 22, c). Internal structure composed of spicules 

 equally confusedly held together by the internal sarcode, tra- 

 versed by the excretory canal-system, which opens at the vents 

 mentioned. Sarcode cancellous, of the same colour as the 

 surface. Spicules of two kinds, viz. skeleton- and flesh- 

 spicules. Skeleton-spicule of two forms, viz. : — 1, large, tri- 

 radiate, in which the fourth arm or shaft is only represented 

 by a short extension of the central canal inside the spicule, 

 or subquadrate, in which this is only extended into a short 

 round elevation or knob (fig. 22, gg), arms round, smooth, 

 sharp-pointed, and somewhat curved, 50- by 4-1800ths inch ; 

 2, long, acerate, fusiform, smooth, sharp-pointed, 117- by 1- 

 1800th inch (fig. 22, h). Flesh-spicules of three forms, viz. : — 

 1, acerate, fusiform, sharp-pointed, slightly curved, miero- 

 spined, varying in size from 6- to 30-6000ths inch long (fig. 



