196 Proceedings of the Royal Irish Academy. 



VII. — Lkptestheria — continued : 



(2) No haft-organ. Rostrum tipped with a slender and apparently mobile 



spine. 



(3) First antennae Estheria-like. 

 {Vj Second antennae Estheria-like. 



(5) Number of pairs of legs comparable to Estheria. 



(G) In males two pairs of claspers. Hand very complicated. Peculiar transfor- 

 mation of the upper lappets of the exopodites in the 10th and 11th pairs of 

 branchial legs in the female to sausage-like appendages— somewhat 

 resembling those found in Limnetis. 



(7) Caudal plate but slightly deflexed, and without any spines above the caudal 

 setae. Posterior segments of the trunk in neither sex with dorsal 

 processes, but ha\ing the posterior edge minutely spinous. 



VIII. — Limnetis : 



(1) Carapace nearly spherical, sraoolli, without distinct beaks or umbones. 



(2) Head very large ; the front region bearing the eyes 'enormous and produced 



into a large rostrum-pointed in female, abruptly truncated in male. Eyes 

 small. 



(3) First antenna minute, slightly elbowed, with indications of three joints. 

 (\) Second antenna, wiih scajx; or base rather short. Flagellae short, scarcely 



longer than scape, but with remarkably long setae. 

 ,5( Ten to twelve pairs of trunk-limbs, upper lappets of the exopodites of the 



nintii and tenth pairs in the female tran^jforiued into cylindrical cords 



bent at the top. 

 (Ii| In nuilc only first pair of trunk-limbs modified as clasping organs. 

 (7) Caudal segmunl blunt, without deutated lamellae or furcae. 



IV. — IJKSCUIITION OF TUB GeNUS LiMNESTHEUIA. 



Of the luatcriai obtained from tlie above-described horizon in the 

 Ardra Iwrc some twenty-four specimens were available, showing body-parts 

 iif suflicicnt similarity to be considered referable to a single genns. Ail the 

 appcmlagcs observed are definitely Eslherian in character, and it would be 

 jKJssible to consider the fo-ssils as belonging to the genus Estheria were it not 

 for the presence of a single distinguishing character of some importance. 

 Claspers were jireisent in six of the specimens, wliicli were thn.s shown to be 

 males, and in eath of these six there was only a single pair. 'J'hat the 

 second j>air, which are characteristic of Estheria, could have been present 

 and unobserved is rendered very improbable from the perfect state of 

 preservation of the pair seen. It is necessary, therefore, to set up a new 

 genus for the reception of lhe.se fossils : — 



LIMNESTHERIA gen. nov. 



Caraj>ace bivalve, pii>i>aiily inmni. Valves oval, of the order of 5 mm. in 

 length, with fringed or ciliated margin. 



