14 



(x. O. SARS. 



[No. 1. 



from each other by a very deep notch or incision, as in the genus 

 Estheria, aud between both, ou the veutral side, the oral orifice 

 is located. 



The preoral part of the head is alniost triangular in form 

 and strongly compressed toward the edges, or surrounded by a 

 thin and high crest, faintly curved dorsally aud forming at the 

 end an obtusely rounded projection. corresponding to the rostrum 

 in the genus Estheria. This terminal projection is finely serrate 

 along the upper side. two or three of the denticles occurring far- 

 thest anteriorly, and partly extending along the lower^edge, being 

 somewhat stronger and more remote from one an other than the 

 rest, which are exceeclingly small and densely crowded. The 

 inferior edge of this subdivision of the head is in its anterior 

 part rather thin and sharpened; posteriorly however it becomes 

 more obtuse. and expands at the base of the labrum, on either 

 side, to a rounded prominence, partly obtecting the base of the 

 autennulæ (see figs. 4, 5). Of any distinct ,,fornix", arching over 

 the base of the antennæ, no trace can be detected. 



The postoral part of the head is composed of only the man- 

 dibular segment and distinctly marked off from the succeeding 

 division of the body dorsally, where a well-defined and mov- 

 able articulation occurs just in front of the dorsal prolonga- 

 tion, connecting the body with the shell (see Pl. II. fig. 1). 

 Anteriorly. it is likewise very distinctly defined from the preoral 

 part of the head by the above-mentioned occipital incision. 

 The dorsal surface of this part is evenly vaulted, whereas the 

 inferior side becomes wholly concealed by the mandibles. 



The eyes are united to a single globular organ, as in the 

 Cladocera, located within the preoral subdivision of the head,, 

 somewhat nearer the rostral than the occipital part and rather 

 remote from the dorsal edge. It is of moderate size : and 

 exhibits. when viewed from above (fig. 3) or below (fig. 4),. 

 posteriorly a very slight sinus, indicating its original duplicity. 

 As to structure. it closely agrees with that of the Cladocera, 

 beiug surrounded by a thin hyaline membrane, and exhibiting 

 numerous crystalline cones imbedded at the base within a dark 



