SUPPLEMENT. 



163 



Vol. II. p. 11. — Terebratula cranium. North of Hebrides, 

 170-650 f. (W. B. Carpenter and Wyville Thomson). I have 

 examined all the Mollusca procured in this important expe- 

 dition. F. Certainly T. euthyra of Philippi, judging from a 

 comparison of one of his typical specimens in the Vienna Mu- 

 seum ; Messina (Seguenza) ; glacial and postglacial deposits in 

 Norway (Sars and others) ; Uddevalla (Crosskey and Robert- 

 son). E. Loffoden I., 300 f. (Sars) ; coasts of Northern Asia 

 and Japan (A. Adams) ; outside Vigo Bay, in about 60 f., 

 two small dead specimens (M'Andrew) ! I frequently observed 

 this Brachiopod turn round on its stalk (like a vessel swinging 

 at anchor with the tide), apparently in order to improve its 

 position for the purpose of feeding. Does this stalk or byssal 

 plug represent the foot of most Conchifera ? The valves, on 

 being touched, close with a snap. The brachial cirri resemble 

 those of T. caput-serpentls in shape and flexibility. I could 

 not detect any fringe of tentacles on the edge of the valves in 

 T. cranium. It has a loop, although of a peculiar structure. 

 With the able and kind assistance of my friend Dr. W. B. 

 Carpenter, I have lately examined more thoroughly the skele- 

 ton or shelly framework. It is formed on the same general 

 plan as that of Waldheimia australis ; but the loop in T. 

 cranium can onlv be seen when the animal is in its natural 

 place, because the upper portion of the skeleton (which is not 

 unlike a horseshoe in outline) is connected with the lower 

 portion on each side by a slight suture that is easily ruptured. 

 When the animal matter is removed by careful boiling in 

 potash-water, the upper portion of the skeleton becomes sepa- 

 rated from the lower portion at or near the bend of the loop 

 on each side where the sutures connect them ; and the fixed 

 or permanent part of the framework consists of two scythe- 

 shaped processes or blades, which are attached by their hafts 

 to the hinge-plate. The terminal points in front of the 

 horseshoe piece are furnished near the sutures with a few 

 unequal-sized and irregularly arranged spikes or projecting 

 teeth. The position of the sutures is not constant, the turn 

 of the loop sometimes remaining with the horseshoe piece, 

 sometimes with the longitudinal processes, and being occasion- 



