Natural History of the British Seas. 839 



seas the temperature of the water is higher at some depth 

 than near the surface. On the other hand, we find in a re- 

 gion farther to the south than Britain, an outlier of the Celtic 

 fauna preserved in the bays of Asturias, where it was dis- 

 covered in 1849 by Mr MacAndrew ; a very remarkable fact, 

 and one appealed to by the Lecturer as confirmatory of his 

 theory of an ancient coast extension between Ireland and 

 Spain. 



There is still much to be done in the investigation of the 

 natural history of our seas, and many districts remain for 

 more minute exploration. It is chiefly among articulate 

 animals, and especially among worms, that fresh discoveries 

 may be looked for. Yet even now new and remarkable forms 

 of mollusca may occasionally be procured ; and during the 

 autumn of last year, in a cruise with Mr MacAndrew, no 

 fewer than twenty additional mollusca and radiat-a were dis- 

 covered in the Hebrides, and have Just been described by the 

 Lecturer in conjunction with Professor Goodsir. Among 

 these is one of the largest, if not the largest, compound Asci- 

 dians ever discovered. In our southernmost province, 

 fresh and valuable remarks have been conducted during the 

 past year by Professor Acland and Dr Cams, who selecting 

 the Scilly Isles as a field for exploration, have filled up a 

 blank in our fauna. 



{To be continued in o-ur next Number.) 



Optical Examination of several American Micas. By B. SlL- 

 LIMAN, Junior, A.M., M.D., &c. Copy communicated by 

 the Author, 



Prior to the publication of the second edition of Dana's 

 Mineralogy, little had been done in distinguishing the several 

 species among American micas, and in allotting them to the 

 various localities. In connection with Professor Dana, the 

 writer, during the passage of the Mineralogy through the 

 press, made a number of observations respecting the optical 

 properties of such micas as were at that time accessible. A 



y2 



