﻿SPONGES.-HALLMANN. 



or become broadened and flattened (frondiform) and more or 

 less subdivided. In any case the uppermost part of the 

 sponge consists chiefly, of separated digitiform terminals, 

 which are usually tapered 

 .and somewhat pointed, 

 and are provided apically 

 each with one or a few 

 oscula. The larger speci- 

 men (Plate xxi., fig. 3), 

 which measures 130 mm. 

 in height, consists almost 

 entirely of frondiform 

 components ; the smaller, 

 if digitiform. In its dried 

 condition, the sponge is 

 particularly dense, hard 

 and tough ; although the 

 amount of shrinkage has 

 seemingly been but slight. 

 The surface is smooth, 

 but slightly uneven owing 

 to the presence of dis- 

 continuous undulations 

 and obscure ridges, 

 which, however, may be 

 due to contraction. In 

 addition, the sponge is 

 provided with small scat- 

 tered verruciform up- 

 wardly directed eleva- 

 tions ; these are some- 

 times fairly numerous on 

 the upper margins of the 

 more flattened upgrowths, 

 but, generally speaking, 

 their occurrence is irre- 

 gular and it is not certain 

 that they are a constant 

 feature. The colour of 

 the sponge is yellowish- 

 grey. 



The precise arrange- 

 ment of the skeleton is 



not apparent in the present condition of the spec-imcns owing 

 to the distortion which it has undergone, consequent upon 

 drying. It is only possible to refer in general terms to its 

 main features {e-i^-, as exhibited in longitudinal section of a 







Fig. 2 5 — Spirastrella alcyonioides. 

 a Tylostyle. a Ditto, (basal ex- 

 tremit}'). b Spiraster. 



