T R I D A C N A 



Plate V. 



Species 4. (Fig. a. b, c, Mus. Cuming.) 



Teidacna Kl'Dls. Trkl. testii ijiljboso-ovatd, ritdi, qiiadri- 

 ad ynin.fjue-coitatd, cudh hitiusculis, pariim elevalis, 

 radiatiiii Uraiis. si/iiavia/ls, srp<a?nis tiuiiierosii), vaUVf 

 irregularibus, hie illic conthiuis, costanim ti/terslitiis 

 aiiffustis, radiatim Uratis ; tilbd. 

 The rude Tridacxa. Slicll gihbously ovate, rude, t'our- 

 to five-ribbed, ribs rather In'oad, but little raised, 

 radiately ridged, scaled, scales numerous, very ivi-e- 

 gular, here and there continuous, interstices between 

 the ribs narrow, radiately ridged ; white. 

 Hub. Philippine Islands ; Cuming. 



The shells figured in this plate represent a very charac- 

 teristic form of Tridariia. certainly distinct from T. squa- 



mosa, and apparently distinct from T. t/ii/as. They ha\e 

 not the anterior obliquity which is peculiar to /. i/ii/aa, as 

 shown botli in the large specimens, Plate I., and the small 

 specimens given in Plate II. Another feature in T. riidis is 

 that the ribs are conspicuously radiately ridged tlirough- 

 out between the scales. The scales are very irregidar, 

 running in some places continuously over the intercostal 

 furrows, and the wliole shell is singularly uncouth and 

 unsymmetrical. 



In the species represented at Plate II., Fig. 1 b, c, which 

 I take to be the young of T. gigas, there are no radiating 

 ridges between the scales , and the shell is characterized 

 by the same obliquity of the anterior portion seen in the 

 larger shell tinured in Plate I. 



June, 1862. 



