of South Devon and South Cornwall. 471 
5. A. polyoum, Hassall. 
Torbay, between tide-marks, encrusting shells of Trochus 
cinereus. 
The form here intended, which I believe to be distinct from A. 
hexagonum, seems to agree with the Sarcochitum polyoum of 
Hassall. There is no sufficient ground for separating it from 
the genus Alcyonidium. 
2. ARACHNIDIA, nov. gen. 
Polyzoary membranaceous, forming a delicate network ; cells 
separate, distant, adnate, connected by a creeping, anastomosing 
fibre. 
A. hippothooides, nu. sp. Pl. XVI. fig. 2. 
Cells lozenge-shaped, or rudely fusiform, of a light horn-colour, 
with fibrous processes round the margin; orifice near the 
upper extremity of the cell. 
On shell, Torbay. 
The Arachnidia may be regarded as an Alcyonidium with its 
cells detached from one another, and held together by a delicate 
thread, instead of being immersed in a fleshy crust. Occasion- 
ally the cells are massed together, but usually they are separated 
by considerable intervals, and connected by a fibre which passes 
off from the two extremities and from about the middle of eachside. 
The habit of the Hippothoa is curiously imitated by this species. 
The form of the cells is somewhat irregular, and the fibrous 
processes round the margin are not easily detected, unless the 
specimen can be viewed with transmitted light. When the 
Arachnidia spreads over the surface of a shell, it is almost impos- 
sible to make them out. 
[On a Cyprina, dredged off the Isle of Man (7. H.); on shell 
and the test of an Ascidian, Lulworth Cove (Mr. Alder).] 
Fam. Vesiculariade. 
1. Vestcutaria, J. V. Thompson. 
V. spinosa, Linn. 
Not uncommon amongst the Brixham trawl-stuff; “deep 
water off the Deadman, rare” (Couch). 
[Filey, Yorkshire; Lytham, Lancashire; Llandudno, North 
Wales. | 
2. Amatuta, Lamouroux, 
A, lendigera, Linn. 
Very common: in great luxuriance on Halidrys siliquosa, 
under the rocky shores of Salcombe Bay, &e, 
30% 
