Linnean Societj/, 599 



the river Ex. It is supposed to be the fish called Ombrina in 

 the Mediterranean; the Sciana cirrhosa^ Linn., Umbrina of 

 Cuvier. 



A Paper was read on The generic characters of Formicaleo 

 of Dr. Leach, with the Description of two new species ; by the 

 Rev. Lansdown Guilding, B.A., F.L.S., &c. 



The writer states, that although the larvae swarm under every 

 rock and shelter in the island, not a single perfect insect has 

 been found flying abroad. The two new species are, 1. Form. 

 Leachiiy fuscescens, flavido-maculatus, alis hyalinis, subfalcatis, 

 immaculatis ; neuris ciliatis : oculis cupreis, pedibus pallidis : 

 and 2. Form, tarsalis, nigro-fuscescens, flavido-maculatus, alis 

 hyalinis, immaculatis, subfalcatis; neuris interrupte nigris; stig- 

 mate nigro : pedibus flaventibus, atro-variis. It inhabits De- 

 merara. 



Dec. 4. — A Paper On the locomotive Power of the Snail ; by 

 Mr. James Main, was read. The authour mentions the follow- 

 ing species as having chiefly come under his notice ; Limax 

 maximus, Lim. ater, Lim. lichenivorus, Lim. rufus, Lim. muta- 

 bilis, Lim. tenax, and Lim. agrestis. The belly of the snail 

 being perfectly smooth, there are no appendages to do the oflice 

 of feet ; and the whole of the body moves at once, and not in 

 parts successively. By placing the animal on a piece of glass, 

 Mr. Main was enabled to observe a muscular motion ; but this, 

 instead of being from head to tail, was directly the reverse, so 

 that the animal's motion cannot be caused by impulses in the 

 direction of its progress. He gives, in conclusion, two conjec- 

 tures as to the cause of the animal's motion; namely, 1st, that 

 the body is moved forward by the retromissive discharge of 

 slime, which, being emitted simultaneously from every part of 

 the under surface, he conceives may exercise a force adequate 

 to the propelling of the animal : or 2ndly, from its power of 

 forming its lower surface into segments of circles along the whole 

 of its length ; and thus, by assuming a vertical vermicular action 

 on the plane of the sustaining surface, impelling the body for- 

 ward by alternate contraction and expansion. As dry air de- 



