200 



probably varying from 13 to 19 mm.; his example was 15 mm. 

 Three differences appear. My species is more concave along 

 the post-dorsal border, shows only bare traces of umbo-rostral 

 lirae, and has no te«th in its right valve projecting beyond the 

 vertical plane. Mr. Hedley tells me he has the same shell 

 from 250 fathoms, off Sydney. 



Cuspidaria (Cardiomya) pinna, n. sp. PL xiii., tigs. 5 to 7. 



Shell squarely oval, ventricose, rather thin, umbos in- 

 flated, rounded, approximate. Front dorsal border short, 

 straight, scarcely convex, joining by a rounded slightly ob- 

 tuse angle the straight barely incurved anterior end. This 

 with a faint angulation joins the open-curved ventral bor- 

 der, which, after a definite incurvation, unites with the lower 

 border of the rostrum. The post-dorsal border is feebly-con- 

 cave to the end of the rostrum, which is rounded at its rather 

 attenuated end. 



The sculpture is very bold. Three distant valid round 

 ribs curve from the umbo to the posterior third of the ven- 

 tral border. In front of these are about seventeen subequal 

 less prominent rounded ribs, equal in width to their inter- 

 spaces. Behind them are two rather distant, less valid ribs, 

 and three more extend from the umbo to the end of the 

 rostrum. All these ribs furrow the inside of the shell, and 

 all crenulate or scallop the ventral border in the ratio of 

 their size and distance. The border of the rostrum is not 

 scalloped. There are microscopic accremental striae, most 

 marked and erect towards the end of the rostrum. Imme- 

 diately beneath the umbo is a small triangular cartilage pit, 

 wider than high. In the right valve is a triangular laminar 

 posterior lateral tooth, with a slight furrow forward to the 

 pit and backwards nearly to the rostrum. Anteriorly, there 

 is a long invalid lamina just within the border. The left 

 valve has an anterior lamina, which forms, with its front 

 dorsal margin, a shallow furrow to receive the lamina of the 

 right valve. The post-dorsal margin of the left valve and 

 its anterior lamina form a straight line, only interrupted by 

 the notch of the cartilage pit. 



The left valve lies inside the right valve throughout its 

 post-dorsal border ; the right valve lies inside the left, mark- 

 edly along the posterior two-thirds of the ventral border, 

 barely along its anterior third, and distinctly along the 

 straight anterior end, where the right valve has a rather more 

 concave edge than the left. 



Dim. — Antero-posterior diam., 6*5 mm.; umbo-ventral, 

 4*1 : section of united valves, 2"75. 



