SIPHONIA.— HALLIEHOA. 67 



Siphonia, for there are cylindrical sponges, probably belonging to Scytalia or Pity- 

 viatella, in which it is also present. 



This species appears to be very abundant in the Upper Chalk of this country. It 

 is very probable that most of the sponges so common in the flints at Brighton belong 

 to this species. The flattened summit and the wide aperture and rounded margins 

 of the cloaca readily distinguish the form from the S. Jicus. 



Distribution. Upper Chalk : Flamborough, Yorkshire ; near Brighton, and in other 

 localities in the Soutli of England, 



SiPUONIA, sp. 

 Distribution. Upper Chalk: Beckhampton. Chalk Marl: Ringmer. 



Subgenus Halliriioa, Lamouroux, 1821. 



Hallirhoa costata, La77ix. (Plate XIV. figs. I, la, lb, Ic, Id, 1 e.) 



1821. Hallirhoa costata, Lamx. Exp. metliod. des Polypiers, p. 72, t. 78. £. 1. 



1831. Polypotliecia bi-septemloba, E. Bcuett, Org. Rem. Wilts. 1. 1-5. 



1847. Hallirhoa costata, Miclielin, Icou. Zoopli. p. 127, t. 31. f. 3. 



1854. Siphonia lobata, Mantell, Medals of Creation^ vol. i. p. 231, f. 4. 



1878. Hallirhoa costata, Queiistcdt, Petref. vol. v. p. 426, t. 135. f. 14. 



1878. Hallirhoa costata, Zittel, Studien, II Ab. p. 79. 



Sponges simple, very variable in the form of their bodies or heads : the simpler 

 examples are conical and partially lobed at the base ; the more complex are depressed 

 spheroidal, and divided vertically into a varying number (from three to seven) of 

 lobes, which occasionally show traces of subdivision. The summit in the lobed 

 individuals is flattened or gently rounded. The stem is relatively slender, crooked, 

 and with root-like processes at its extremity. The body of a small specimen is 

 42 mm. in height by 57 mm. in width, whilst a large individual measures 78 mm. 

 in height by 150 mm. in width. The longest stem which I have seen measures 

 180 mm. 



The cloaca is cylindrical or funnel-shaped, with angular margins ; its depth varies 

 in different individuals^in some examples it is not more than 15 mm. below the 

 surface, or about one fourth the vertical height of the body, whilst in others it 

 appears to penetrate to the central portion of the body. The larger canals are 

 1-5 mm. in width; those immediately beneath the cloaca are straight; exterior to 

 these the canals follow a curved course to the cloaca. The smaller canals, which 

 extend in an arched direction from the exterior surface to the interior of the sponge, 

 are -7 mm. each in width. In weathered specimens numerous canals are exposed on 

 the upper surface, radiating from the margins of the cloaca. 



The spicules forming the interior mesh have mostly smooth arms, but their 



