828 Mil. il. a. JACKSON OW TillC 



{?)) Key to the gemis Ligidiuin. 



The diagnoses of the genera TyjMoUgidium and Ligidium s.s. 

 are taken from Vcrhoeft"(1918) with one omission. 



A. Eyes siiiil boili'-pigineiit absent. Antennal Hagelliim 19-23 segments. 

 Miindiljles willi large interval between tbo biting teeth luul ti-itiinitiug part ; 

 in intervening space lU-11 hairy bristles. Urojiods widely separated. 



Subgeiins Ti/pJiloliffiJium Verb. 

 One species, T. coecum (Crimea — caves). 



li. Eyes large, body-pigment well developed. Antennal flagellnni 10-15 segments. 

 Mandibles with 3-5 hairy setae, tlieir biting teeth and triturating i)art not 

 widely separated Subgenns Lit/idium Verb. 



r With bristle group on hind lateral border of 1st 

 • l.< somite 2. 



(.Without bristle group C. 



., ( With lateral depression on hind border of 1st somite 3. Kuropo). 



"'X Without lateral depression geymanicum (Central 



., ( Surface covered with little knobs nodtilosum (Caucasus). 



■ t Surface smooth and shining 4. 



I C Endopod of urojiod longer than exopod hij^morum (Europe). 



' 'X I'jxopod longer tlian enclopod 5. 



, ( l^'rontal grooves deep and distinct hosniensc C^. ISosnia). 



°' ii. L'^rontal grooves absent or very shallow fra/filc (Caucasus). 



,. ( Surface rough and scaly lalnm (California). 



( Surface smooth and shining 7. 



C Inner process of propodite of uropod .shorter than 



7.-] breadth of base japonicum (Japan). 



(, Inner process longer than bre.idth of base 8. 



„ C Endopod less than one-sixth longer than exopod... gracile (California). 



\ Endopod about half as long again as exopod loiit/icandatuta (New 



York). 



(4) The gemis Ligidiiun. 



The diagnosis given below is modified from Sars (1899). 



Body oblong oval, moderately convex, attenuated behixid. 

 Oephalon without lateral lobes. Mesosome with coxal plates 

 marked oflf from tergite by faint semicircular grooves on last four 

 somites. Metasome moderately small and abruptly contracted, 

 without produced postero-lateral angles on last somite. Eyes 

 large and compound. Antennula of 3 segments, small, distal 

 segment rudimentary, but distinctly projecting in front of head. 

 Antenna with midti-articulate fiagellum of 10-15 {Ligidium) or 

 19-23 (Tgphloligidium) segments. Mandible with Jacinia mobilis 

 and 3-5 {Ligidium) or 10-11 {Typhloligidium) setose bristles 

 between it and the molar tubercle. 1st maxilla with 3 stout 

 setose bristles on interior lacinia. 2nd maxilla membranous, 

 with 2 stout setose bristles ou inner side. Maxillipede with 

 endopod of 5 distinct segments ; inner blade linguiform and 

 setose. Legs very slender and greatly increasing in length 

 posteriorly. Opercular plates of pleopoda very thin, without any 

 obvious branchial structure. Uropoda moderately lax'ge, base 

 produced on inner side into a process upon which the endopod is 

 set ; endopod usually longer and more slender than exopod and 

 provided with 2 long and slender apical bristles. 



