FEEDING MECHANISM 



441 



The first endite of the maxilla together with the more dorsal spines of the first endite 

 of the maxillule and the gnathobasic process of the mandible point directly upwards 

 into the mouth. 



A summary of the above comparison between the feeding mechanisms of P. vidua 

 and D. levis is shown in the following table (see Fig. i) : 



Food stream through shell pro- 

 duced by 



Food collected by 



Food entangled by 



Food mass passed by mandible 

 on to 



Food mass passed from maxillule 

 on to biting mouth-parts which 

 are 



Food prevented from escaping 

 and pushed back on to mouth- 

 parts by 



During bottom feeding food may 

 be scraped up by 



P. vidua 

 Vibratory plate of maxillule 



Mandibular palps 

 Labral gland secretion 

 Maxillule 



Gnathobasic coxopodites of man- 

 dibles 



First trunk limbs 



Antennae 



D. levis 

 Vibratory plate of maxilla 



Mandibles 



Labral gland secretion 



Endopodite of maxillule 



Three endites of maxiliules, two 

 endites of maxilla and part of 

 exopodite of maxilla 



First trunk limbs 



Mandibles 



SKELETON AND BODY WALL 



The body wall of Doloria, apart from the valves and limbs, is, as in all Ostracods, 

 excessively thin. The appendicular system attains its stability through two separate 

 skeletal organizations — a series of narrow articulating sclerites which radiate from the 

 attachment of the adductor muscle to the valves, and a rigid system comprising the 

 upper lip and powerful endoskeletal structures connecting the latter to the adductor 

 muscle. The adductor muscle is thus the centre of stability for the whole body. 



In considering the mechanics of the body, it may be divided into two portions — a 

 soft flexible dome covering the back between heart and caudal furca (Plate VI), and 

 the ventral half to which the limbs and furca are attached (Fig. 2). The latter can again 

 be divided into two parts — the anterior which supports the eyes and limbs, and the 

 posterior caudal furca. 



ENDOSKELETON AND SCLERITES 



The anterior limb-bearing portion centres round the massive upper lip. The labrum 

 is helmet-shaped, and is encircled completely about its equator by a slightly thickened 

 chitinous ring. Postero-laterally this thickening becomes more massive and extends 

 around the sides and back of the mouth. It thus forms the anterior margin of the hypo- 

 stome, which consists of an oblong plate with the longer axis lying transversely. From 

 its anterior corners there project inwards a pair of massive tubular endoskeletal struc- 

 tures which extend dorsally and, at their upper ends, turn sharply at right angles towards 

 the middle line but do not meet (Figs. 2, 3). Their upper portions are embedded in the 

 tendon of the adductor muscle (Figs. 4, 5) which forms the hinder portion of a com- 

 plicated endosternite. They have been termed by Miiller (1894, p. 19) and others the 

 "Sternalaste i ". I am naming them the "anterior hypostomal apodemes". 



