FORMS ALLIED TO SARON 397 



than one-third the length ; two pairs of dorso-lateral spines ; posterior margin with two 

 pairs of spines, the inner pair very large, and four pairs of long setae, of which the outer 

 three are feathered. Antennule with narrow pointed stylocerite. Antennal scale broad, 

 with outer apical spine. Mandible with incisor process and rudimentary unsegmented 

 palp. Maxillule, proximal endite narrow; endopod small, curved, with two setae. 

 Maxilla, endite i very much shorter than endites 3 and 4, with a small lobe representing 

 endite 2 ; proximal setae of exopod not very long ; endopod small and slender. 



Maxillipede i, exopod with five setae on basal part, and six distal; coxa and basis 

 large ; epipod large, with small anterior lobe like a rudimentary podobranch. Epipod of 

 maxillipede 2 as that of maxillipede i, with anterior lobe representing a podobranch. 

 Exopod of maxillipede 3 large, with six setae. Small epipods present on legs 1-4, 

 but no trace of arthrobranchs. Legs i and 2 not free from moult, but carpus of 

 leg 2 distinctly divided into three segments, segments i and 3 very much smaller 

 than 2. 



Although this specimen is not perfect most of the characters of systematic importance 

 can be established ; but it cannot be definitely stated that the carpus of leg 2 shows the 

 final segmentation ; or that the arthrobranchs may not appear in later stages. Judging 

 by the development of Spirontocoris cranchii and S. occulta (Lebour, 1936) one would 

 expect the carpus to be divided from the first to the full, or nearly the full, number of 

 segments found in the adult, and it is improbable that there would be no trace of arthro- 

 branchs, if the adult possesses them. According to the keys to the genera of Hippolytidae 

 given by Caiman (1906) and Kemp (1914) the combination of characters found in this 

 species is not found in any known genus. The larvae are so exactly like those of Saron 

 that there cannot be a doubt that they belong to a genus related to it ; but no such genus 

 is known which lacks arthrobranchs. The resemblance to the larvae of Latreiites is rather 

 close, but Latreutes and its allies have a mandible without palp or incisor process. The 

 lack of a palp is not a character of much importance, since in the two very closely allied 

 species Spirontocaris cranchii and S. occulta (Lebour, 1936) the latter has a palp while 

 the former has not; but the absence or presence of an incisor process seems to be a 

 character of primary value. 



One point is of rather special interest in this developmental series, namely the small 

 number of stages. In most Hippolytidae known there are as many as nine stages 

 (Lebour, 1936, p. 99), but these may be greatly abbreviated as shown above for 

 Chorismus which has three only. In the present form there are only four, but stage I is 

 a perfectly normal larva with quite small rudiments of the legs. In Hippolyte proteus 

 there appear to be four stages (Gurney, 1927) instead of the nine which Miss Lebour has 

 found in H. varians. 



A total number of nine stages is found commonly among Caridea, and is not known 

 to be exceeded. It is interesting to note that both Eraser and John in their admirable 

 accounts of the development of Euphausidae (1936) agree in finding three Calyptopis 

 and six (or rarely seven) Furcilia stages, the term Furcilia being used to include all 

 stages between Calyptopis and post-larval. Accepting, then, the interpretation of 



