236 Mr. W. King on some Shells and other Invertebrate Forms 



I have only got one specimen of the so-called Saxicava sul- 

 cata of Smith, which is generally considered a large form of Saxi- 

 cava rugosa. My specimen is the size of that figured by Mr. 

 Lyell in the ' Philosophical Transactions ' for 1835, pi. 2. fig. 24. 

 Mr. Lyell states that Capt. Bayfield has found it alive in the Gulf 

 of St. Lawrence, and I believe it occurs in all the fossiliferous 

 localities already mentioned. 



My specimens of My a uddevallensis * are identical in every 

 particular with those figured by Mr. Lyell in his paper " On the 

 Fossil and Recent Shells collected by Capt. Bayfield in Canada f." 

 It differs from My a truncata in being shorter, " and the posterior 

 truncation oblique and inclined to the basal margin, and with a 

 smaller sinus in the muscular (pallial) impression J." It occurs 

 in a fossil state at Uddevalla, in Canada, in Northern Russia, and 

 in the basin of the Clyde ; and it is still living in the Gulf of 

 St. Lawrence §. 



All my specimens of the foregoing shells have very much the 

 appearance of the Norwich crag and Uddevalla fossils — a circum- 

 stance which, viewed in connexion with what has just been stated, 

 and the fact that none have yet been found living in the locality 

 where they occur, is strongly in favour of the conclusion that 

 they are pleistocene fossils. As far as I can learn, they were 

 brought up from a shell-bank situated about twenty-five miles to 

 the east of the Fern Islands. If my inference respecting the age 

 of these fossils be correct, it is necessarily proved, that the place 

 where they occur was covered with the sea during the pleistocene 

 period. 



Halichondria mammillaris = Spongia mammillaris, Muller. 



This sponge does not appear to be common on our coasts. Of 

 two specimens which I have procured, one was brought up by 

 the lines from deep water ||, and the other I dredged in fifty fa- 

 thoms. The base of either does not exceed an inch in diameter ; 

 the mammillations are three-quarters of an inch in length. 



Halichondria, nov. spec. ? 



As the sponge under consideration has some characters in com- 

 mon with Halichondria ficus, which is " liable to some modifica- 



* So called in Prof. E. Forbes' valuable paper " On the Geological Re- 

 lations of the existing Fauna and Flora of the British Isles." Vide Memoirs 

 of the Geological Survey, &c, vol. i. p. 407. 



+ Geological Transactions, 2nd ser. vol. vi. pi. 16. figs. 5 and 6. 



X Ibid. p. 137. 



§ Ibid. 



|| By the expression "deep water " must be understood a depth ranging 

 from forty to eighty fathoms. The greatest depth given in Nome's Chart of 



