and temarkahle North-Atlantic Brachiopoda. 251 



two funnel-shaped processes, which diverge from the beak 

 in the upper or larger valve, and of two hlade-likc processes 

 besides an uj)right j)late or septum in the upper part of the 

 lower or smaller valve. 



Its nearest ally is Rhynclionella^ from which it appears to 

 be distinguishable only by the straight instead of incurved 

 beak, and by the ai-ms or brachial apparatus not being coiled. 



Atretia gnomon *, Jeffreys. 



Shell triangularly oval, compressed, thin, semitransparent, 

 and rather glossy : sculpture^ a very few slight and indistinct 

 longitudinal ridges, and numerous close-set microscopic im- 

 bricated scales : coloitr white : margins broad and rounded in 

 front, sloping gradually at the sides, and acute-angled behind : 

 beak in the upper or larger valve somewhat prominent: fora- 

 men triangular and groove-like, narrow, and exhibiting inside, 

 below the beak (as in llhynchonella 2)sittacea)^ a series of 

 arched septa or laminar marks of growth : hyssus cylindrical : 

 deltidiuni well defined: hinge-plate strong: teeth in upper 

 valve two, resting on a triangular funnel with its mouth or 

 opening outwards ; in the lower valve there are also two teeth, 

 which are nearly straight, slender, and blade-like : sockets 

 deep : skeleton composed of an erect and thin triangular crest 

 or septum in the middle of the lower valve, like a sun-dial- 

 stile, which is pointed at the top, besides the above mentioned 

 processes in each valve ; on either side of the septum are two 

 slight parallel ridges which extend from the hinge, and a 

 diverging ridge towards the lower end of the septum. L. 0'25, 

 B. 0-2. 



A single living specimen occurred in lat. 63° 9' X., long. 

 56° 43' W., at a depth of 1100 fathoms, clayey mud. It was 

 attached by thebyssus to a fragment of a tubular Foraminifer, 

 and covered with a cluster of young Atretia' in different 

 states of growth, and a dwarf form or variety of Trunca- 

 tulina lohatida. Valves and fragments were also found in 

 lat. 59'^ 10* N., long. 50° 25' W., and in lat. 56° 11' N., 

 long. 37° 41' W., at depths of 1750 and 1450 fathoms. Im- 

 perfect valves had been dredged by me during the ' Porcupine ' 

 Expedition of 1869, in stations 20 and 30, at depths of 1443 

 and 1380 fathoms, off the west coast of Ireland. This curious 

 Brachiopod was noticed and figured by Mr. Davidson in his 

 Supplement to the ' Monograph of the British Fossil Brachio- 

 poda' (Publications of the Palajontographical Society, 1874), 

 ]i. 7, pi. i. figs. 7-10 ; but the restoration from the imperfect 



* Having a septum like the hand or stile of n sun-diul. 



