130 DE. T. DAVIDSON ON RECENT BRACHIOPODA. 



septa, which adhere to the sides of the hinge-plate, and are more or less confluent with the 

 valve. Labial processes folded into four lobes, united by a membrane, forming a 

 brachial disk with long cirri. Mantle extending to the margin of the valves, and 

 closely adherent. A tu.berculated flattened margin surrounds the valves. In the 

 interior of the ventral valve a triangular plate occupies the posterior portion of the inside 

 of the fissure, and from under the centre of which extends a short mesial septum. Shell- 

 structure punctate. Colour dull yellow or white. Length 3 lines, width 4 lines, depth 

 2 lines. 



Hab. Mediterranean Sea ; J]]gean Sea, at a depth of from 27 to 100 fathoms (Forbes) ; 

 Straits of Samos ; Atlantic coast of Spain and of France, off Cape Breton, in upwards 

 of 45 fathoms, two miles east of Guernsey, 18 fathoms ; off Madeira in 20 fathoms 

 (M° Andrew) ; Canary Islands ; Rhodes (Fischer) ; Guetaria in 80 fathoms (Hidalgo). Costa 

 informs us that Argiope decollata occurs plentifully near the islands of Capri, Ischia, 

 Palmieri, and in the Gulf of Taranto. The 'Challenger' Expedition obtained it in great 

 abundance at Gomera, off Teneriffe, in 73 or 75 fathoms. 



It is a common fossil in the Upjier Tertiaries of Italy, Sicily, Malta, and is found at 

 Nice and elsewhere ; also in rocks of Miocene age. 



Ohs. Dr. S. P. Woodward and myself were able to give the first description and illus- 

 trations of the manner in which the loop and brachial appendages are arranged in this 

 important genus and species (Ann. & Mag. Nat. Hist. vol. ix. May 1852). Since then 

 Dr. Gray proposed to separate from the genus Argiope all those forms with a single 

 submarginal septum, uniting them into the subgenus Cistella. Up to the present time 

 we are acquainted with only a single recent species of Argiope, but there are several 

 fossil species referable to the genus. 



In his admirable memoir ' Eecherches sur I'Organisation du Manteau chez les Brachio- 

 podes articules,' p. 29, 1864, M. E. Deslongchamps asserts that, properly speaking, 

 no pallial apparatus (of spicula) exists in the genus Argiope. The whole of the mantle, 

 which is stretched like the skin of a drum between the arched branches of the dorsal 

 valve, is pervaded merely by an amorj)hous calcareous substance, the presence of which 

 is indicated by a slight effervescence when the mantle is submitted to the action of dilute 

 acid. The labial appendages and their cirri are equally devoid of definite calcareous 

 structures, although their yellowish aspect in dried specimens might lead at first sight 

 to a contrary supposition. If, however, the raised up j)ortion of tlie mantle in the larger 

 valve be examined at tlie place wliere it forms the walls of the visceral cavity, a con- 

 centric line of detached spicula may be seen when sufficiently magnified, elongated 

 perpendicularly to the direction of the front, and nearly similar in aspect to those of 

 Kraussina. Some small calcareous particles of an angular and irregular shape may also 

 be seen. The genus Argiope thus shows a manifest passage from a mantle entirely 

 destitute of calcareous bodies to one where spicula are more or less numerous, as 

 in Terebratulina, Terehratula, Kraussina, Megerlia, and Ilorrisia. 



In his "Note sur quelques especes nouveUes de Megathi/rides," Bull. Soc. Zool. de France, 

 vol. viii. 1883, M. J. de Morgan strongly advocates the adoption of A. d'Orbigny's generic 



