Revision of the Genus Lomanotu.s. 215 



Us description the original descriptions of the remaining 

 rive, omitting most of the purely generic characters and 

 all specific characters derived from colour, the evidence will 

 present itself in its clearest form. None of the six species 

 is better suited for this purpose than L. genei, as none has 

 been more fully described from mature examples. Let this 

 then be taken as the standard, and the following table will 

 exhibit all the structural differences which can be adduced as 

 justifying the retention of the remaining five species Verany's 

 character of the genus, drawn from the < Revue ZooWique ' 

 of 1844 and the Acts of the Milan Congress of the same year, 

 published in 1845, is placed at the head of the table for 

 reference. 



Lomanotus, Verany (1844). 



A c? 1f ° bI ° n 8> ^edge-shaped ; head as wide as the body, furnished with 

 4 small entacuhform prolongations; dorsal tentacles 2, retractile cluh- 



Sf&iSSSft!^ mC i U f d in a , cal y ciform s heath ; bmnchi* formed 

 of 2 irregularly fringed and festooned membranes, attached longitudinally 

 one to each side of the dorsal surface and to the tentacle-sheath j anal and 

 genital orifices on the right side. ' 



L. genei, Verany.-Sheath-margins 4-lobed ; pleuropodium reaching 

 almost to the tail on either side. 3 



L. marmoratm (Alder & Hancock).-Sheath-margins entire; pleuro- 

 W U Sthem° mieCt Wlth th ° SheathS ' but P roduced forwards in 



L.favidus (Alder & Hancock).-Sheath-margins tubercled; pleuro- 

 podium indistinct its place marked by°a marginal serieT of 

 unequal-sized papilla. B 



L. Portlandieus, W. Thompson.-Sheath-margins divided into six finely 

 pointed filaments ; pleuropodium « commencing in front of the S 

 of the sheaths and continuing behind the termination of the tail." 



L. hancocki, Norman.-Sheath-margins with 5 divisions; rhinophores 

 httle longer than the sheaths, not laminated. 'opnoies 



L. «™»- Trinchese .-Pleuropodium continuous round the body from 

 sheath to sheath, its two lateral sections uniting at the apex of Sie 

 tail and forming there a fin-like swimming-organ. 



At a first glance it would seem as if specific value might 

 airly be conceded to the structural distinctions shown in this 

 table. But when we come to examine into their claims more 

 narrowly in the light of the facts brought out by the chrono- 

 logical survey just given, it will be seen that many of these 

 characters lack the necessary certainty and permanence In 

 studying a group of soft-bodied animals such as the Nudi- 

 brancb. Mollusca, endowed, and often to a high degree, with 



