ORAL APPENDAGES OF MARINE ISOPODA. 69 



pointed ones, and an inner series of thinner, more slender, usually sharply 

 pointed ones, which have one or more rows of teeth on their sides, which 

 vary considerably in number and size. The two series are frequently 

 separated by a long, slender, sharply pointed spine. There are often a series 

 of setse on the anterior outer (and sometimes inner) border. 



The inner lobe shows considerable variation in the different genera. It 

 consists of an elongated, narrow, posterior portion, which widens anteriorly 

 into an oval or more or less triangular, flattened plate, with two to four 

 setaceous spines at the distal extremity, in addition to which, one or more 

 setules may be present. In a few cases the number of setaceous spines may 

 be greater on the appendage of one side than on that of the other. 



The Masdllipedes. — Each maxillipede consists of a divided coxopodite, a 

 basipodite with a short inner lobe on the inner side, and an outer lobe or 

 palp (endopodite) articulating with the basal segment on the outer side. On 

 the outer side posteriorly there is a wide, more or less oval, plate, the epipodite. 

 The divisions of the coxopodite lie respectively posterior to the epipodite and 

 basipodite. The inner lobe of the basipodite is generally fringed distally 

 with a number of setose and plain spines, and on its inner side and about its 

 middle is a curved process which serves to hook together the appendages of 

 the two sides. Occasionally there are two or more of these processes. 



The outer lobe or palp is composed of a varying number of joints, but the 

 first or " collar "-joint, a short one immediately anterior to the basipodite, is, 

 1 believe, present in most genera. It would seem to be absent according to 

 Miss Richardson (21) in the genus Chiriscus, for no such joint is shown in 

 the figure of the maxillipede of Chiriscus australis, Richardson. 



In Edotia, Guerin-Men., Synidotea, Harger, Chiridotea, Harger, and 

 Macrochiridothea, Ohlin, there are three joints in the palp of the maxillipede ; 

 in fdotea, Fabricius, Erichsonella, Benedict, Colidotea, Richardson, Eusym- 

 merus, Richardson, Synisoma, Collinge, and Euidotea, Collinge, four joints are 

 present ; whilst in Crabyzos, Spence Bate, Mesidotea, Richardson, Pentidotea. 

 Richardson, Pentias, Richardson, Zenobiana, Stebbing, Glyptidotea, Stebbino-, 

 Paridotea, 'Stebbing, Cleanti'ella, Richardson, and Engidotea, Barnard, there 

 are five divisions in the palp. 



It is very doubtful whether the structure of these parts indicates in any 

 way the phylogeny of these Crustacea. In any attempt therefore to estimate 

 the value of these appendages for purposes of classification due consideration 

 should be paid to the segmentation of the metasome, and also to any 

 evidences of degeneration or special modification. 



It may be interesting to roughly classify the known genera according to 

 the segmentation of the metasome and the number of joints of the palp of 

 the maxillipede. 



The primitive Idoteida3, in all probability, possessed a metasome composed 



