326 Bulletin Vanderbilt Marine Museum, Vol. VII 



the cell is usually of much smaller diameter than the interior of 

 the cell, prohibiting removal of the shell without injury. The 

 mantle is richly coloured and very frilled. Dr. Hedley gives a most 

 interesting photograph of a model of the burrow of Tridacna 

 crocea cut open to show the natural position of the shell and ani- 

 mal, with the extended foot that excavated the cell, also a photo- 

 graph of the mollusk embedded in a block of Astrean coral and a 

 series of photographs of young T. crocea. Messrs. Whitley and 

 Boardman (1929) have published an unusual photograph made 

 by Mr. Boardman at Low Islands, Queensland, of living specimens 

 of T. crocea burrowing in a block of coral rock. 



One of the "Alva" specimens is shown in plates 138 and 139. 



Dr. Hedley (1921) has given an excellent revision of the Aus- 

 tralian Tridacna, which contains an extensive synonymy of the 

 present species. Dr. Prashad (1932), in reporting the "Siboga" 

 mollusks, has added to this. 



Tridacna crocea possesses considerable variation in the shape 

 of the valves, the degree of their tumidity and of sculpture. The 

 squamae ornamenting the ridges varies from fragile, elevated 

 scales to worn off lines on the surface. 



References : Pectunculus striatum, etc.. Lister, M., Hist. Conch., 

 1685, pi. 353, fig. 190. 



Chama imhricata, Chemnitz, J. H., Conch. Cab., 1784, p. 124, 

 pi. 49, fig. 496. 



Tridacna crocea, Lamarck, J. B., Anim. sans Vert., 1819, vol. 

 VI, p. 106.— Hedley, C, Proc. Sect. D, Austral. Assoc. Adv. 

 Sci., Brisbane, 1900, vol. XII, p. 348; Rec. Austral. Mus., 

 1921, vol. XIII, No. 4, p. 166, pi. 29, fig. 5, pi. 31, fig. 9, pi. 32, 

 fig. 1, pi. 34, figs. 13, 14. — Whiteley, G. P., and Board- 

 man, W., The Austral. Mus. Mag., April-June, 1929, vol. Ill, 

 No. 10, p. 230 and text figure. — Prashad, B., Siboga-Expedi- 

 tie, Monogr. LIII-c, 1932, Lamellibranchia II, p. 292. 



