46 CORBULID.E. 



cular cardinal : in the left valve a small, sunken and triangular 

 cardinal, besides a long but slight laminar lateral on the pos- 

 terior side : inside glossy and nacreous, closely but obscurely 

 lineated lengthwise; edges sharp: jnuscidar scars triangular, 

 lying near the dorsal margins. L. 0-325. B. 0-375. 



Habitat : In mud among boulders^ 40-45 f., close 

 to Croulin Island^ and in another part of the Sonnd of 

 Skye; rare. Mr. Dawson found a worn and imperfect 

 valve in sliell-sand from Haroldswick Bay in the north 

 of Shetland. Coralline Crag (S. AYood) ; newer tertiary 

 beds near Antwerp (Nyst and Westendorp) . Koren 

 got it at Bergen ; M^ Andrew and Sars dredged it off the 

 coasts of Finmark, the former in 45-90 f. ; Deshayes 

 obtained it from Sicily and Bona, and Tiberi at Naples ; 

 Forbes in the ^Egean between 40 and 150 f . ; and 

 :\IMndrew at Madeira in 20 f. 



Clark conjectm'ed that this might be the young of 

 Thracia convexa, and he said that the present species 

 has an ossicle in the hinge ; but he did not see with my 

 eyes. I have compared specimens of P. gramdata and 

 T. convexa of all sizes, fi'om the fifteenth of an inch in 

 length. Each exhibits a marked difference of outline : 

 one is square, and the other triangular. I have also 

 examined perfect examples of the Poromya from Scan- 

 dinavia, Skye, and Naples ; and in none of them could 

 I detect an ossicle or any space for it. He also stated 

 that the siphons of these two mollusca are equally short, 

 and ornamented with cirri or filaments ; but neither of 

 these characters was noticed by him in his elaborate 

 account of the only species of TJiracia described in the 

 ' History of the British Marine Testaceous Mollusca," 

 and he admitted that he had not seen the animal of T. 

 convexa or of P. granulata. 



Forbes described the recent shell as P. anatinoides , 



