118 BRITISH TTXK'ATA. 



covered with fragments of shells and sand, especially 

 towards the attached part. Mantle yellowish green. 

 Tentacular filaments numerous and stont. Branchial 

 sac with papillae at the intersections of the meshes, 

 and occasionally small intermediate ones on the longi- 

 tudinal bands or bars. Oral lamina plicated on the 

 right side. 



Lengtli. An inch and a half to two inches. 



Hub. Deep water. 



ENGLAND. Mr. Alder has met with one or two 

 Asc.idiK from the coasts of Northumberland and Dur- 

 ham which we are inclined to refer to this species. 



SCOTLAND. [Hebrides (Alder, 1865).] Outer Haaf, 

 Shetland, dredged (Norman & Jeffreys). [Forty miles 

 east of Whalsey Lighthouse, 1861, the type specimens 

 (Norman, 1868).] 



First 'rrford. Alder, 1868 [: coll. Norman & Jeffreys, 

 1861]. 



The test of A. j_>l<jn-ia (PI. XI, fig. 3), which is rather 

 thin, soft, and transparent, is amply supplied with 

 blood-channels, the terminations of the small branches 

 being slightly enlarged and rounded. The mantle is 

 delicate and is but scantily provided with muscular 

 fibres which are scattered and irregularly disposed. 



The primary vessels of the branchial sac (PL XI, fig. 

 4, and PL XVIII, fig. 3) are pretty regular in size and 

 arrangement, and the secondary have the stigmatic 

 meshes rather large. The minute plications of the 

 vascular web are wide and shallow, and there is 

 usually a longitudinal bar corresponding to each pli- 

 cation. The reticulation formed by the liars and the 

 primary vessels is rather coarse and nearly equilateral, 

 and the papilla? which are at the intersections are con- 

 sequently somewhat distant ; they are large, conical, 

 and obtuse ; there are also here and there minute 

 papillae on the bars between the large ones, and the 

 membrane in connexion with the latter is rather limited 

 in extent. The oral lamina is widish, and the ribs, 



