96 Mr. H. J. Carter on the 



TUBELLA*. 



Gen. char. Skeleton-spicule curved, fusiform, sharp-pointed 

 or rounded at the extremities, smooth or spined. Statoblast 

 globular or elliptical ; aperture lateral or terminal ; crust 

 composed of the granular microcell-substance mentioned, 

 charged with ingequibirotulate spicules — that is,alittle trumpet- 

 shaped spicule having a straight shaft which is smooth, spined 

 or inflated, or both, terminated by a large disk at one, and a 

 small one or an umbonous, circular, marginally spined head 

 at the other end (PL V. fig. 7, i) ; the former applied to the 

 chitinous coat, and the latter forming part of the surface of the 

 statoblast. 



1. Tnhella paulula. (PI. VI. fig. 10, or-c.) 

 Spongilla paulula,lSk,, No. 20, p. 15, pi. xxxviii. fig. 8. 

 Thin, incrusting. Surface even. Structure fragile, crum- 

 bling. Colour now brown. Skeleton-spicule curved, fusi- 

 form, abniptly sharp-pointed, spiniferous or smooth. Stato- 

 blast globular ; aperture sunken, infundibular ; crust com- 

 posed of granular microcell- structure charged with two kinds 

 of ingequibirotulates, one form of which is much stouter than 

 the other, and consists of a straight shaft passing by trumpet- 

 like expansion into the large disk, which often has radiating 

 lines, and abruptly terminating in the other, which is only one 

 fourth of the diameter of the former (PI. VI. fig. 10, a, h) ; the 

 other form similarly constructed, but more delicate, with the 

 shaft inflated towards the large disk, and the smaller one much 

 less in proportion than in the larger form (fig. 10, c) ; the forms 

 not mixed but confined to their statoblasts respectively ; ar- 

 ranged perpendicularly, with the large disk resting on the 

 chitinous coat, and the smaller one forming part of the surface 

 of the statoblast. 



Ohs. Although the skeleton-spicule in Dr. Bowerbank's 

 illustration is smooth, it is stated in his diagnosis (p. 16, 1, c.) 

 to be " entirely spined," which is the case generally, but not 

 always ; so that the artist must have taken for the illustration 

 one of the smooth ones. 



2. Tubella spinata^ Carter, n. sp. 

 (PI. VI. fig. 9, a-m.) 



Thin, coating, spreading. Structure fragile, crumbling. 

 Colour light brown. Skeleton-spicule curved, fusiform, gra- 

 dually sharp-pointed, smooth or spiniferous. Flesh-spicule 

 minute, curved, fusiform, thin, gradually sharp-pointed, 



* Tubella, a little straight trumpet. 



