374 



THE ATLANTIC. 



[chap. v. 



upward to a width at tlie top of 40 mm. A deep cavity passes 



from the upper open end 

 down to the stem -like con- 

 striction. The outer surface 

 of tlie sponge is raised into 

 spiral ridges somewhat as in 

 Euplectella, and under the 

 ridges are irregularly spiral 

 lines of large holes. The in- 

 terior of the cup presents a 

 very remarkable character, 

 which reminds one at once of 

 many of the chalk ventricu- 

 lites. The inner layer is deep- 

 ly fluted, thrown into a series 

 of alternating vertical grooves 

 and ridges, so that the out- 

 line of the cavity in a trans- 

 verse section is deeply sinuous. 

 The substance of the sponge 

 throughout is composed of a 

 close anastomozing net -work 

 of siliceous fibres ; toward the 

 outside the net-work much re- 

 sembles that of Ajj/u'ocallistes, 

 while on the inner wall the 

 structure is trellis -like, and 

 the form of the meshes square 

 and more regular. The spaces 

 of the net - work are crowded 



Fig. loo. — Lefroyella* decora, Wyvim.e Thom- . . - . - 



SON. Natuiai Size. (No. 56.) With siuall regular hexactiuel- 



* I have associated with this species the name of our icirni friend His Excellency 

 Major-general Lefroy, C.B., F.R.S., Governor of Ber.nudus. 



