On Subaquatic Insects. 129 



singular minute brachelytrous insect, which he has described under 

 the name of Diglossa mersa, and in which the powerful structure of 

 the tarsi, tarsal claws, and mandibles, as well as the ciliation of the 

 legs, indicate a mode of life similar to that of Aepus. 



My friend, Dr Johnston of Berwick, whose investigations upon 

 the submarine invertebrated animals have led him to explore the sea 

 coast in his neighbourhood with so much success, has also met with 

 the Aepus near that town. And in the same situation he discovered 

 several specimens of another brachelytrous insect, together with seve- 

 ral small coleopterous larvae and pupae, which he has been so good as 

 to place in my hands. These were all taken from under rocks with- 

 in tide mark, fully 200 feet below high-water mark, and within 50 

 feet of low water mark, and where at each tide the rocks are co- 

 vered for four hours or thereabouts. 



The perfect insects in question prove to be undescribed, belong- 

 ing to none of the genera hitherto established in the sub-family 

 Omalides, to which they are referable. The very minute size of the 

 elytra are quite characteristic of the insect, distinguishing it from 

 all the other Omalides, in some of which the elytra nearly cover the 

 abdomen, being of a larger size than usual in this group. 



Genus, Micralvmma,* Westw. (Plate IV.) 

 Corpus oblongum, depressum, lateribus abdominis marginatis. An- 

 tenna? mediocres, extrorsum crassiores. (Fig. 1 e.) Palpi maxilla- 

 res articulo ultimo prsecedenti longiori, elongato-conico. Thorax 

 postice angustior, capite paullo latior, lateribus rotundatis. Elytra 

 minuta, segmentum primum abdominis vix tegentia. Pedes graci- 

 les. Tibice extrorsum inermes. Tarsi simplices, longe ciliati, ar- 

 ticulis ultimis elongatis, reliquissimulsumptis eequalibus. (Fig. 1,J^) 

 Ungues simplices, haud basi recurvati. 



Slructura oris Labrum transversum, margine antico ciliato et 



trilobato lobis fere aequalibus et rotundatis. (Fig. 1, a.) Mandibular 

 elongato-trigonaa, acutae, marginibus extends nonnihil arcuatis, se- 

 tigeris, interno fere recto impressione sub apicem. (Fig. 1, b.) Max- 

 illoe (Fig. 1, c.) elongatae, curvatae, bilobatse, lobo interno gracili 

 apice acuto intus setoso, externo majori sub apicem articulato. Palpi 

 maxillares maxillis fere duplo longiores, 4-articulatae, articulo lmo 

 brevissimo, 2do triplo longiori ad apicem crassiori, 3tio praecedenti 

 duplo breviori, obconico ; ultimo longitudine secundi elongato-co- 

 nico. (Fig. 1. g.) Mentum transversum, antice paulo angustius? 

 lateribus subrotundatis, angulis seta longa. instructis. Labium 



* M/xgo;, parvus, et KaXu,u,//,a, tegmen. 



