144 



AMERICAN JOURNAL 



Fig. 22. 



Fig. 22. Mcgathi/ris decollaia, \^, haemal valve and animal. 



Genus MEGATHYRIS, D'Orb. 

 Mantle adherent to the shell. Foramen and area large. 



Subgenus Megathyris, D'Orb. 



Megathyris, D'Orb., Pal. Fran. Ter. Cret. 1847, p. 147. 

 Prod, ii, p. 259. An. Sci. Nat. 1848. 



Argiope, Desl., 1842 (not Savigny), Mdm. Linn. Soc. Norman- 

 die vol. vii, p. 9 ; Bull. Soc. Geol. Fran, vii, 2nd Series, 

 p. 65. Dav., Int. Class. Brit. Brach, p. 72 ; Mem. Lin. 

 Soc. Normand. vol. x, 185G, p. 137; P. Z. S. 1852, p. 

 81; An. Nat. Hist. 1852, p. 372, 1861, p. 39. Rve., 

 Conch. Icon. pi. x; Journ.de Conchyl. 1861, p. 135. 

 Woodw., Rec. and Foss. Shells, p. 220. Chenu, Man. 

 de Conchyl. ii, p. 209. H. and A. Adams, Gen. Rec. 

 Moll, ii, p. 580. Bronn, Malac. iii, pt. i, pp. 304, 306, 

 309. 



Orthis, sp. Phil., Hagen. Mich., not Dalman. 



Terebratula, Lam., Blainville, &c. (sp.) 



Ariomia, Chemn., Gmel., Muhlf., &c. (sp.) 



Shell transversely oblong, or semicircular ; smooth or ribbed 

 with more or less prominent radiations ; strongly punctate ; 

 hinge-line wide ; area flat ; foramen large, triangular or rounded ; 

 deltidium absent or rudimentary ; interior of hsemal valve fur- 

 nished with from three to five, or more, rounded submarginal 

 septa, over which the broad loop is bent and attached. The 

 brachia are continuous and follow the course of the loop, and 

 hence appear four-lobed. The cardinal process is large and 

 strong, centrally excavated. The interior of the shell is pustu- 

 lose. 



The name Argiope was proposed in 1827 by Savigny and 

 Audouin (Descr. de 1' Egypt, ed, ii, xxii, p. 334, pi. ii, fig. 6), 

 for a genus of Egyptian spiders, typified by Aranca lobata, Pall. 



