150 



Tjiis species differs from M. crassicostata by its narrower 

 shape, depressed uinboiies, and subacute ridges, and by tbe 

 absence of a subanterior contraction ventrally. 



Mytilicardia platycostata, E. M. Johnston. 



Reference. — Proc. Roy. Soc. Tasm. for 1879, p. 40. 



" Shell oblong ovate, ornamented with twelve broad slightly- 

 raised squamose radiating ribs, surmounted by a smaller ridge 

 of distant lamellose spines ; breadth of interspaces and rays 

 equal ; rays finer and closer together as they approach the slope. 

 Long., 50 mil. ; lat., 35 mil. ; alt. (both valves), 26 mil. Eare, 

 Table Cape." E. M. Johnston. 



Mytilicardia curta, spec. nov. PI. ii., fig. 9. 



Shell trapeziform, anteriorly very short, extremely gibbous ; 

 ventral margin straight, with a slight insinuation anteriorly ; 

 posterior margin roundly truncated ; roundly elevated 

 diagonally from the umbo, the posterior and dorsal portion 

 somewhat dilated and convex ; the ventral side is compara- 

 tively narrow and precipitous. Surface ornamented with 22 

 narrow, rather compressed, scaly, radial ribs ; interstitial 

 spaces slightly narrower than the ribs, marked with regular 

 transverse lirfe ; margin of valves coarsely crenulated. 



Dimensions. — Length, 18 ; greatest width towards the pos- 

 terior margin, 11 ; width through the umbo, 8 ; thickness 

 through both valves, 11 millimetres. 



Locality. — Adelaide bore. 



This species, which has a general resemblance to Cardita 

 trapezia, Bruguiere, makes through C. scahrosa, mihi, an ap- 

 proach to the genus Cardita. 



Genus Caedita. 



stis-opsis of species. 

 Triangular; ribs, 15, granose. C. trigonalis. 



Ovate-triangular ; ribs, 22, thin. C. pecten. 



Eotund ; ribs, 24, granose, linear interspaces. C. compacta. 

 Ovate-quadrate ; ribs, 20, thick, crenulated. C. Murrayana. 

 Oval-subquadrate ; ribs, 30, with erect scales. C. scahrosa, 

 Eotundly heart-shaped ; ribs, 22, spinosely serrated. 



G. spinulosa. 

 Eoundly oblong ; ribs, about 30, with lamellar scales. 



C. gracilicostata. 



id., widened posteriorly. C. latissima. 



id., narrowed anteriorly ; ribs, 37. C. polynema. 



Eoundly oblong ; ribs, less than 30, with granulations. 



Eibs, 26 ; fine granulations. C. delicatula. 



Eibs, 22 ; coarse granulations. C. Tasmanica. 



