NOTES AND QUERIES. 309 



at this season account for its peculiarly brilliant appearance. It possesses 

 the very unpleasant character of having an extremely disagreeable odour, 

 even whilst alive. I presume that the reason why fish are very rarely 

 described in their true colours by ichthyologists is that they do not see 

 their specimens until they are dead and have lost their colours, but this is 

 the brightest coloured Rock-cook I have ever seen. — Thomas Cornish 

 (Penzance). 



CEPHALOPODA. 

 Octopus at Penzance.— During the week ending July 16th I took two 

 specimens of Octopus vulgaris in my nets, in about eight fathoms water. Of^fi^- 

 They were both small ones, the largest less than three feet in length. '^ 

 Both had ink-sacs full of the ordinary fluid, but they did not attempt to 

 squirt it when taken. In fact, I never saw an Octopus attempt to squirt. 

 One was beautifully coloured at the time of its capture, mottled light and 

 dark sepia-colour. The other was dull self-coloured when captured, but 

 attahied this mottled appearance as it died. — Thos. Cornish (Penzance). 



MOLLUSCA. 



Secretion of a violet-coloured fluid by certain of the LimnEeidae. — 



My friend Mr. Wm. Nelson (Leeds) noted in the ' Quarterly Journal of 

 Conchology' for May, 1877, that Limnma stagnalis had the power of 

 emitting, when irritated, a pale violet-coloured liquid, which he had 

 noticed on taking the animal (after killing) from the shell, and also when 

 lifting them alive from out of the water. It may be of interest to know 

 that both L. peregra and L. palustris also possess this peculiar property, 

 which I have frequently noticed in living specimens. The liquid discharge 

 is of a much darker colour in palustris than that in peregra. — W. E. 

 CoLLiNGE (Springfield Place, Leeds). 



Rate of Progress by Snails. — The rate of progress in the land 

 Mollusca is so slow, that to travel "at a snail's pace" has become 

 proverbial. It would seem from experiments recently made by an American 

 savant, at the Terre Haute Polytechnic, that the precise rate has been 

 approximately determined. Half-a-dozen snails were allowed to crawl 

 between two lines ten yards apart, when the average speed was ascertained 

 to be at the rate of a mile in fourteen daj's. The particular species of 

 Helix is not named. It would be well to have stated this, for doubtless 

 some species can travel ftister than others. 



CRUSTACEA. 



Livid Swimming Crab at Penzance. — I have to-day taken a crab 

 which I must describe as the " Livid Swimming Crab." It precisely 

 coincides with the descriptions given by Bell of P. marmoreus and of 



