TEREBRATULINA. 13 



state, where they sometimes almost disappear from the regular convexity of the valve ; 

 margin flexuous ; in the young the valves are less convex. Imperforated valve deepest 

 near the umbo, forming at times a rounded, elevated ridge, extending to the front, a cor- 

 responding depression or shallow sinus existing in the larger valve ; while, in other 

 specimens, a mesial longitudinal depression exists in the smaller valve. 



The surface is ornamented by a great number of radiating little ribs or costae, 

 fewer, coarser, and simple in the young, augmenting rapidly in number at a more 

 advanced period by bifurcation, and by the intercalation of a number of small plaits, 

 intersected by regular concentric strias, strongly produced in young specimens, giving the 

 shell a granulated appearance, these becoming less distinct as the animal advances in age. 

 The internal calcareous supports in smaller valve short and anneliform ; the muscular 

 impressions are marked ; no mesial longitudinal septum is perceptible on either valve ; 

 then internal edges minutely crenulated ; structure punctuated ; colour squalid white. 

 Dimensions variable: length 11, width 7, depth 5 lines. 



Recent and Fossil. 



Obs. This species of shell and its animal has been ably described by Professor Forbes 

 in his work on ' British Mollusca :' "The arms or buccal appendages occupy the greater part 

 of the cavity of the shell. They are fixed to and follow the course of the apophysary skeleton, 

 and appear when the shell is forcibly opened in the form of a pair of brilliant orange or crimson 

 fringed loops, lodged in each half of the cavity of the imperforated valve; the outer margins 

 of each loop bear long cirrhi, also of a brilliant orange or crimson hue, and though the 

 arms themselves cannot be protruded, their cirrhi are very extensile : when the animal is 

 lively, the two valves separate and gape, for no very great distance from each other in 

 front, and from their sides are seen the long crimson cirrhi, extended like a pair of double 

 fringes, and borne somewhat stiffly, and with a slight curve outwards. Towards the edge 

 of the strongly adherent mantle attached to each valve, are placed at regular intervals 

 about forty small cirrhi of a softer texture, which do not appear to be protruded, at least 

 conspicuously, beyond the edges of the shell : these cirrhi are tinged with crimson ; also at 

 their bases are seen, when a high magnifying power is used, coloured dots and cavities with 

 vibrating corpuscules, which may be regarded as ocelli, and otilitic capsules. The whole 

 surface of the mantle is studded with vibratile cilia. On each side of the inner surface of 

 the perforated valve is seen an ovarium of an oblong shape and brilliant vermilion colour; 

 and extending beyond these ovaria, in radiating fashion, are the glandular masses of 

 the liver." 



In the recent state it is one of our commonest Brachiopoda, first found by Dr. Fleming 

 at Ullapool in Loch Broom, afterwards dredged by different collectors at Oban ; on the 

 West Coast of Scotland, Loch Fyne ; at Lismore, near Oban, off Armadale, in the Sound 

 of Skye, forty miles West of Zetland, &c, in depths varying from ten to fifty fathoms. It 

 is likewise found in many spots throughout European seas, presenting slight variations in 

 different localities. In the fossil state, it occurs in the Coralline Crag of Sutton, where 



