B. W. PRIEST ON THE CALCAREA. 101 



bottle, comprises at present only one genus, Leucosolenia, of Bower- 

 bank, the knowledge of this Family being very imperfect in com- 

 parison with the other three, and also being the simplest form of 

 Calcareous Sponge, whose walls are pierced by simple canals, the 

 Sponges themselves forming simple sacs, with a completely flagel- 

 lated endoderm, or inner membrane, the walls being composed of 

 ectoderm, mesoderm, and endoderm, the formation of which we 

 shall see further on when treating briefly with the embryology of 

 the subject. This Family may be simple, branched, or united into 

 a common stock, Leucosolenia botryoides; (Bk.), belonging to it. 



The Syconido?, from the Greek %ukov, a fig, sponges of this 

 family formerly being likened to the shape of that fruit, comprises 

 six genera, Sycon (Nissa), Grantia (Fleming), Ute (0. Schmidt), 

 Amphoriscus (Hasckel), and the two new genera Heteropegma and 

 Anamixilla (Polejaeff). The Sponges of this Family are mostly 

 solitary, with thick walls, which are pierced by straight radial 

 tubes, the latter in some species projecting on the surface as conical 

 prominences, Grantia compressa and ciliata (Bk.) belonging to this 

 Family. 



The Leuconidce (from Aevkos, white) comprises the following 

 genera: — Lcucilla and Leucetta (of Hseckel), Leuconia (Bk.), and 

 the new one, Pericharax (of Polejaeff). These sponges have thick 

 walls, which are pierced by branched channels, and remind one 

 more of the complicated water canal systems to be found in the 

 non- Calcareous sponges, Leuconia nivea (Bk.) belonging to this 

 Family. 



The Teiconidce (Teichojiia, Carter) contains two genera, both, 

 the latter especially, being comparatively new, viz., Teichonella 

 (Carter) and Eilhardia (Polejaeff). 



The Sponges are peculiar in that the differentiation of the outer 

 surface is divided into two quite different parts, that bearing oscula 

 and that bearing pores. 



In 1878 Mr. Carter described and figured a species from Aus- 

 tralia, Teichonella prolifera, a specimen of which was also dredged 

 at Bognor by the Rev. Henry Fase, I think in 1880, which he 

 kindly gave to me along with others. I have not heard of its being 

 found before or since on our shores. 



As I mentioned just now, the walls of the Calcareous Sponges 

 are composed of three layers, the ectoderm, mesoderm, and endo- 

 derm. The ectoderm, or outer membrane, is composed of flattened 



