246 WILLIAM BLAXLAND BENHAM. 
liani, Intraclitelliani, Postclitelliani, Aclitelliani, have already 
been given above. 
The extent of the clitellum varies considerably in the same 
genus, even in the different specimens of the same species 
when fully developed; for instance, in Lumbricus agricola 
it occupies six or seven somites, xxx to xxxv1; in L. rubellus, 
somites xxvi to xxx1I (seven somites); in L. trapezoides, 
somites xxvir to xxxv (nine somites); whilst in L. (Allurus) 
tetraedrus it occupies only six somites, from xx11 to xxvil. 
Amongst the Intrachitellian forms the same variation is to 
be noted: Anteus has as many as fifteen somites, xv to xxIXx, 
making up the clitellum; Titanus has nine somites, xv to 
xx111; Urocheta has ten somites, x1v to xx111; Geogenia 
has ten somites ; whilst Rhinodrilus has only three somites 
in this structure, x1x, xx, xxI. It commences as far forwards 
as somite 1x in Geogenia. 
In Eudrilus the three different species each have a different 
number of somites in the clitellum, E. decipiens having only 
three, x111, xiv, xv; whilst E. Lacazii has six somites, x111 to 
xvitt, to form this organ. In Rhinodrilus the girdle is com- 
plete, whilst in the other forms it resembles Lumbricus in 
having a saddle shape. 
Amongst the Postclitellian genera there are usually fewer 
somites occupied by the clitellum, which is a complete girdle, 
and nearly always commences with somite x1v (Pericheta, 
xiv, xv, xvi; Plutellus, x1v to xvi1; Acanthodrilus, xiv 
to xvi1, and others), or in x11 (Perionyx, x11I to xvi, and 
Pontodrilus, x1t to xvit); in x11, in Kinberg’s genera 
Rhodopis and Mandane, or in xv, in Pontoscolex. (In 
Kinberg’s genera, Nitocris, Amyntas, Lampito, Phere- 
tima, the clitellum appears to commence at somite xiv, and 
this character with the numerous sete to each somite would 
justify us in considering them as forms of Perichzta.) 
Rhodopis, if Kinberg’s description can be considered of 
any value, possesses the shortest clitellum, occupying only two 
somites, as is also the case in Pericheta bicincta. 
The position of the clitellum and the position of the gizzard 
