402 Messrs. Alder and Hancock on a proposed New Order 



LiMAPONTiA NIGRA, JohnstoTi. PI. XIX. figs. 4, 5, 6. Johnst. 

 in Loud. Mag. Nat. Hist. vol. ix. p. 79. 



Body black, or sometimes of a transparent brownish green, 

 rather depressed, the sides slightly 6verhanging the foot. When 

 in full progression the sides are almost parallel, but more fre- 

 quently they are a little convex, and when the animal is at rest 

 it becomes nearly circular. Head truncated in front and flat at 

 the sides, where it is elevated into two crest-like ridges, arched 

 from behind forwards. Et/es large, situated at the posterior ex- 

 tremity of the crests, in a pale circular space, which is prolonged 

 on the crest. Foot of a yellowish colour, slightly stained by the 

 viscera ; narrower than the body ; the sides are parallel, and it 

 tapers gradually to a bluntish point behind ; in front it is trun- 

 cated wdth the angles rounded. Length 1| line. 



A single specimen was obtained by Dr. Johnston in Berwick 

 Bay ; since which it has been found in great abundance by 

 Mr, Cocks at Falmouth, in small pools among the rocks, between 

 half-tide and high-water marks, feeding upon Conferva glauces- 

 cens. We have also got it in similar situations at Cullercoats, 

 and Mr. Richard Howse has taken it at Whitburn. 



The following observations on this species have been commu- 

 nicated to us by Mr. Cocks : — " They are found on Conferva glau- 

 cescens; they eat its branches and the microscopic larvae with 

 which the plant is infested. In July 1847 I procured a portion 

 of the Conferva, not more than one inch in length and four- 

 eighths in breadth, containing upwards of twenty patches of 

 spawn; each patch contained from 50 to 150 ova. Stragglers! 

 are sometimes met with on the Conferva albida ; but the spawn, 

 never. I have found them in the shallow pools on the rocks at 

 half-tide in the months of April, May, June, July, August, Sep- 

 tember, October, and November. In December I visited all my 

 old haunts, but without success : the slugs had migrated, and the 

 Conferva was in a decayed state or dead. In fine W'arm weathei 

 they congregate on the surface of the Conferva, but in dull, cold 

 or windy weather, they descend towards the lower portion of the 

 plant. They are active, very hardy, and tenacious of life. ] 

 have kept them in bottles for a month or six weeks, withoui 

 changing the water, with apparently vei-y little injury." 



They appear to be most plentiful during the months of Jun< 

 and July, at which time we met with them in great abundance a 

 CuUercoats ; but on visiting the same spot again in the autumn 

 not a single mdividual was to be found. It is probable that th 

 old individuals die off during the winter, and the young broo 

 do not come to maturity until the following year. Their remain 

 ing 80 much longer on the Cornish than on the Northumberlan 



