A IJRMSIUN M^ I UK AISI RAMAN IKIhACNA — HKHI.F.V. l7l 



Ti;i|iA(NA MAXIMA, llnllrii. 



Tii'l'irliin:< iii'i.riiini, Holteii, Mils. Holt.. 17J»S, [t. 171 for ( 'lu-iii II it/,, C'olicli . 

 Cal»., vii., 17SI-, p. ll'J, [.I. xlix., ti^^ liC). 



C/n(iiiti 'jiij'i"., Vitf. li., Dillwyii, l)es»'ri|i. Cat., i,, 1W17, [i. lil 1 : l^iu"\ rinpedit! 

 iiietli., pi. ecxxxv., tig. 1. 



Tiidnnm rhnnfuhi, Hvl'vv, Ckik'Ii. Icon., xiv., Ib6:i, pi. ii., tiL,--. 'In. 1<I.. 

 Hia/.ier, Mem. A list r. Mus., ii., 1889, p. 28. /</., Melvill & SlaiHleii, 

 .I.MiiM. Li. in. S..C. Zoul., xxvii., 1899, p. 189. /-/.. llfdlev, Mem. 

 .Austr. Mus., iii., 1899, p. 505. hi., Hedley, I'roc. liiim. S..c. 

 N.S. Wales, xxxi., 190(5, p. 4.()5 (not 7'. rioinjafa, Laniaick, 1819). 



'rrliLiriiii •■ii,„i,ri'stia, Saville Kent, (ireat Bairier Heel', 189."), pp. 12, 2«), lO.S, 

 pis. iv. and xv. (clams in situ), Clii'onio pi. xiii., Hg. 10 (culouis of 

 mantle margin). /</., BaiiHeld, The Confessions ot a lieaclicouiber, 

 1908, p. 132. 



Triduciia srait/ia, Sowerbv, Tlies. Conch., v., 188-4, p. l8l, pi. cccclxx.xix., 

 Hg. 1»>. 



i'rohably the type shell tiguied hy Chemnitz of V. uct.niini is still 

 preserved in the Copenhagen Museum. 



Ti;ii>ACNA MAXIMA, var. idsson, var. nov. 



(Plate xxix., tig. (i, and Plate xxxiii.. tig. 11). 



A Clam from Queensland and Lord Howe Island apparentl}- differs 

 fnnii typical 7'. nni.n'iii'i by the shortness of the dorsal-posterior end and 

 it is also remarkable for the large pedal gape. The resiliuui is considerably 

 submerged. Indeed, when more material is available for comparison, this 

 may stand as an independent species. The type is a young shell (C. 18727) 

 80 mm. long, which 1 collected at Mast Head Island, Capricoru Group. 

 A large and massive individual of the same species, 195 mm. in leugtli, 

 Avhich I took at Ltnd Howe Island, is shown ou PI. xxix., tig. 6. 



This variety marks the southern limit of the geuus. 



On a recent visit Mr. A. R. McCullocli found this Tn'Jm-iut plentiful 

 on the reef at Lord Howe Island. Specimens ranged from two to eight 

 inches in length, those in unfavourable conditions being considerablv 

 distorted. Fi-equeuth" the TriihtciKt excavated in dead coral rock a hole 

 half an inch deep round the byssal anchoi'. The I'libbed scales of the 

 unibonal area indicate the depth attained. So variable is the colour 

 and pattern of the mantle that no two animal.s seemed alike; they might 

 be uniform dark chocolate or chocolate edged with green or have a paler 

 ground with vivid blue or green markings. 



He observed the Tridaciia to suffer from the operations of a Sea 

 Urchin, Ecli! inHiietra lurntiter Avhicli drives a bnrroAV undei'mining and 

 eventually dislodging the bivalve. Once loosened the Tn'dacna appeared 

 to be unable to re-establish itself and was apt to be washed in to a sandy 

 pool where it quickly perished. 



