DU. BAIRU ON TWO NONDESCRIPT LARTAL ANNULOSA. 247 



late Mr. Cumiug. Their general appearance was peculiar, and I 

 was disposed to place tliem (as Annelids) in a new family, fol- 

 lowing the family Hipponoida^ and to form for them a new genus 

 (a genus of somewhat degraded Annelids) allied in some re- 

 spects to the Amphinomacea. Like some of the genera belong- 

 ing to the family Hippono'idfe, such as Hipponoe, they were des- 

 titute of caruncle, and had apparently the feet disposed in a 

 single row, whilst, as in Lophonota, there was no appearance of 

 either tentacle or antennae. The branchiae seemed to be meta- 

 morphosed into stellate groups of short setae placed in rows on 

 the back, wbere, in the Amphinomacea, the branchiae are usually 

 placed. Several naturalists to whom I showed these animak 

 at once proclaimed them to be marine ; and the general appear- 

 ance of at least the species figured in Plate V. is such as to 

 lead to that conclusion. Upon more mature examination, how- 

 ever, their resemblance to the larval form of some insects struck 

 me; and in one of the species (Plate VI.), where the head was 

 somewhat more exposed, the larval structure of the organs of the 

 mouth became manifest. By pressing these organs outwards, 

 Mr. Tuffen West was able to make a sketch of them in situ (Plate 

 VI. fig. 4) ; and their resemblance to those of an insect larva 

 struck him forcibly at the time. A more careful examination of 

 the sketch so made tends to show that these are not marine an- 

 nulose animals, as I was led at first to suppose, but that in 

 reality they must be referred to the larval state of some un- 

 known insects. Their general resemblance, however, to marine 

 animals, and the belief that the structure of no larvae like these 

 under consideration has ever been published, determined me to 

 bring them before the notice of the Linnean Society ; and as Mr. 

 West has given an exact and very good representation of both 

 species along with a good many details, I thought less apology 

 was required. 



It is perhaps objectionable to give a generic name to the 

 larval condition of an insect, but in the meantime, till we know 

 something more of the perfect insect to which they belong, and 

 the true nature of these creatures themselves, I have given to 

 them the provisional name of Thetisella. 



The genus may be characterized thus : — a row of tubercles or 

 feet on both sides in a single row, upon which are implanted a 

 tuft of strong setae. Two (?) pairs of hooks or feet on the ven- 

 tral surface near the anterior extremity, on the two first tho- 



17* 



