46 corbulidjE. 



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 : muscular 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 Sound of 

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

 valve in shell-sand from Haroldswick Bay in the north 

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

 beds near Antwerp (Nyst and Westendorp). Koren 

 got it at Bergen ; M f 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 iEgean between 40 and 150 f . ; and 

 M f Andrew at Madeira in 20 f. 



Clark conjectured 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. granulata and 

 T. convexa of all sizes, from 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 Thracia 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, 



