210 Mr. P. H. Gosse on the Sloughing of the Spider -Crab. 



The only other British ChemnitzitE which I have not seen 

 alive are the Ch. Barleei, Ch. excavata, Ch. Scillce [Ch. nivosa, 

 which is the Ch. cylindrica (juv.), and Ch. truncatula of authors). 

 Though in a former paper I have included the Aclis unica 

 amongst the Chemnitzia, it may possibly turn out to be of a 

 different type : — this observation is made without further know- 

 ledge on this point ; I know pretty nearly its habitat from ha- 

 ving found recent shells, but with the animal so collapsed as not 

 to emit the organs. I will make no remark on the Aclis ascaris 

 and A. nitidissima, as the animals still elude our researches. 



I have now stated all that I know, agreeably to my views, of 

 this difficult and interesting genus, and corrected some popular 

 errors as well as those of observation, and particularly many of 

 my own ; for however greatly our amour propre may suffer by 

 such admissions, there is absolutely no other alternative but to 

 submit to them, which, if omitted, or not made at the proper 

 moment, would leave us pretty much in the same position as the 

 Chancellor of the Exchequer's regiment of conscience-money 

 payers, which curious public fact, illustrative of one of the 

 mysterious operations of the human mind, if properly pondered 

 on, will suggest to us all, in respect of the pi-esent and the here- 

 after, many salutary, important, and high considerations. 



I am. Gentlemen, your most obedient servant, 



William Clark. 



XX. — On the Sloughing of the Spider-Crab (Maia Squinado). 

 By P. H. Gosse, A.L.S. 



An opportunity having just occurred to me of witnessing the 

 sloughing of a large Crab, I put down the principal points that 

 I observed, hoping that they may throw light upon a subject 

 that has always appeared so full of difficulty; namely, the man- 

 ner in which the limbs are withdrawn from the exuvise. 



As I was out this morning searching for algse and zoophytes 

 at low water, in the little cove of Hele near this town, I 

 looked into a crevice that formed a small tide-pool beneath a 

 huge overhanging rock. In the remotest corner crouched a 

 Spider-Crab {Maia Squinado), face outwards, as is the custom 

 with crabs in such circumstances. On pulling it out, I was 

 astonished and delighted to observe how completely the carapace 

 and the limbs were covered with parasitical zoophytes and algae. 

 A deHcate Ceramium was conspicuous among the latter, and the 

 former consisted of Antennularice and Plumularice in great profu- 



