DE. T. DAVIDSON OX EECEXT BEACIIIOPODA. 185 



lower or ventral valve. Cirri numerous, long an 1 stiff. On tlio under valve the ovaries 

 are of a tawuy hue, as figured by Miiller. Length 9 lines, l)readtli 11 lines. 



Hah. Nortli Atlantic seaboard from Spitzbergen to Vigo Bay* ; in 18-90 fathoms on 

 almost every part of the Scotch and Irish coasts as well as in the seas of Shetland and the 

 Orkneys (J(>ffreys) ; Isle of Man (Forbes) ; Greenland. Prof. E. Forbes says, in liis 

 ' History of British Mollusca,' tliat " this curious bivalve was first added to the British 

 lists by Dr. Fleming, who found it adhering to stones, from deep waters in Zetland ; 

 since then it has been taken abundantly in several localities, chiefly on the Avcst coast of 

 Scotland ; off Arran, in 20 fathoms (Smith) ; Loch Fyne in 30-80 fatlioms, plentiful on 

 stones; off ISIull in 20 to 90 fathoms; off Lismore in from 20 to ;50 fathoms; off 

 Armadale in 18 fathoms; off Copenhaw Head, Skyc, in 40 fathoms; on tlie Ling Bank 

 off Zetland in 50 fathoms (M'Andrcw and E. Forbes) ; Loch Alsh, Loch Carron, Ullapool, 

 East of Lerwick, in 40 fathoms (Jeffreys). In Ireland it has been taken off Youghal by 

 E. Ball, and off Cork by Humphreys." 



Ohs. Specimens of C. anomala vary much in shape, whicli is to a great extent de- 

 pendent on tlie nature of the object to which they are attached. At times a number are 

 clustered together so closely on the same stone that they necessarily become distorted 

 during grow tli. The position of the vertex and the elevation of the upper valve vary 

 also a good deal, as well as the circular wrinkles that cover its surface. Interiorly the 

 muscular impressions also vary to some extent, and, as remarked by Dr. Gwyn Jeffreys, 

 "sometimes the shell is ribbed across or obliquely, having taken the impression of an 

 Astarte or Pecteu on which it has been moulded. Being often affixed to rugged stones 

 or small pebbles, its shape is adapted to the angles and extent of the basal surface. 

 "When it has bare standing-room only, it increases in height and becomes regularly conical. 

 The under valve of specimens attached to a smooth shell of a Pinna is usually a mere 

 film." To small bleached specimens dredged by Jeffreys and Barlee off Shetland in 

 170-530 fathoms, Dr. Gwyn Jeffreys in 1869 applied the varietal name of alha. Two 

 of these specimens were kindly forwarded for my examination by Dr. Jeffreys, but I could 

 not discover any valid grounds for separating them from Miiller's species. The lower 

 or attached valve is entirely concealed by the upper one. (See Plate XXVII. figs. 9-9 b.) 



The intimate structure of the shell of Crania anomala lias been described by Dr. 

 Carpenter in chapter 2 of the Introduction to vol. i. of my ' Monograph on British 

 Fossil Brachiopoda,' and by Prof. "NV. King in his memoir " On the Histology of the 

 Test of the Class Palliobranchiata," in vol. xxiv. of the Trans, of the Ptoyal Irish 

 Academy. Dr. Carpenter sajs,_loc.cit. p. 37, that in Crania norvegica " the shell-structure 

 is widely different from that of Brachiopoda generally. Instead of a series of flattened 

 prisms arranged with great uniformity, Ave only meet with a substance which does not 

 present any regularity or distinctness in the arrangement of its components, but which 

 is not at all unlike that of which many Lamellibranchiate shells are composed, and may 

 probably, like it, be regarded as liaviug been originally formed of the coalescence of cells, 

 which were destitute of any consistency in size, shape, or general arrangement. But 



* Specimens of Crania (C. anomala or C. turhinata"?) -were oLUiincd Lj- the ' rorciipinc ' Expedition in the 

 Mediterranean in from 207-2GG fathoms; in 1869 at Station 2 in 8t>S fathoms, and Station 12 in G70 fathoms; in 

 1S70 at Station 1 in ij(;7 fathoms, and at Station 3 in 600 fathoms (Jeffreys). 



25* 



