360 BULLETIN OF THE 



Molpadia borealis Saks. The differences between my only 

 specimen and Sars's description and figures consist in the smaller num- 

 ber of calcareous granules and in the calcareous plates being somewhat 

 more symmetrical in shape. I do not think the differences sufficient to 

 establish a new species. 



In my specimen the buccal disk is expanded as in Sars's figure, but 

 no tentacles are visible. In the places they ought to occupy fifteen 

 small holes can be counted. Sars never saw any tentacles, although he 

 kept some specimens alive, dredged in 351 fathoms. 



Why Selenka should have made out this species to be the same as 

 my Molpadia oolitica I cannot well understand. My original speci- 

 mens were in his hands, and I have re-examined them lately. The cal- 

 careous granules of M. borealis are small and irregular, in M. oolitica 

 they are larger, always oval, and formed of concentric layers. The for- 

 mer has retiform calcareous plates, the latter none. The former has 

 no visible tentacles, the latter has always distinct simple digitiform ten- 

 tacles, even in mutilated specimens. One of the specimens sent from 

 the Cambridge Museum to Mr. Selenka had received by some accident 

 the label of " Cape Palmas ? " and on this one he has based his new genus 

 Embolus. I am perfectly satisfied that the Embolus pauper Sel. is the 

 same thing as Molpadia oolitica. The figures he gives of the ccsopha- 

 gial ring of Molpadia oolitica and of a calcareous grain of Embolus 

 pauper are both taken from specimens of M. oolitica. The absence of 

 oesophagial ring in the specimen he examined is accidental, as is also 

 the absence of the tail-like prolongation of the anal extremity of the 

 body. 



Cambridge, November, 1869. 



