20G Mr. N. Colgan — Contributions towards a 



the centre of each bay. The pleuropodium declines suddenly 

 as it approaches the anterior extremity of the animal, yet 

 persists as a distinct ridge until it reaches to and effects a 

 junction with the base of the rhinophore-sheath ; towards the 

 posterior extremity it declines gradually, and becomes obso- 

 lete as it approaches the tail. The rosy orange of the body 

 takes a deeper tone in the pleuropodium, yet the tips of the 

 segments or papillae are not distinguished by any marked 

 difference of colour. The deep red viscera of the animal 

 sending off branches (hepatic lobes) on either side to the 

 pleuropodium are clearly visible through the pellucid tissues 

 of the back. The mandibles when treated with caustic potash 

 showed under a £-inch objective a finely cross-hatched or 

 tessellated masticatory margin (Kaurand of Bergh). Under 

 the same power the general character of the radula with its 

 finely serrated teeth-margins was easily made out : unfor- 

 tunately before the examination of this exquisitely constructed 

 organ was completed it was lost by an explosive ebullition of 

 the potash in which it was being boiled over a lamp-flame. 



On comparing this description and the dead animal with 

 Alder and Hancock's Monograph, it became clear that my 

 capture belonged to the genus Eumenis instituted by these 

 authors in 1815 and that it was structurally in close agree- 

 ment with the species 111. marmoratus as described and figured 

 by them in that year. The genus Eumenis having been 

 founded by Alder and Hancock in ignorance of the fact that 

 an equivalent genus Lomanotus had been created by an 

 Italian scientist a year earlier, they subsequently abandoned 

 the name Eumenis in favour of Lomanotus. But close as was 

 the resemblance of the Dublin Bay Lomanotus to Lomanotus 

 (Eumenis) marmorutus, the differences in colour, size, and 

 form were yet sufficient to raise doubts as to their identity. 

 In the Monograph the rhinophore-sheaths of L. marmoratus 

 are described as having simple margins, the pleuropodium is 

 represented as disconnected from the sheaths and continued 

 forward in advance of them, the animal is described as opaque 

 and marbled with dark brown and white, while its length is 

 given as little more than half an inch. It was obviously 

 necessary to make a close study of the literature of the genus 

 before venturing to decide whether the Bullock Lomanotus 

 might safely be assigned to anj r of the established species or 

 should be set down as nondescript. 



The result of this study when made was to show the rarity 

 of most of the species of Lomanotus, the necessarily meagre 

 material on which some of the species had been founded, and 

 the unsatisfactory nature of many of the specific distinctions 



