LARVAE OF DECAPOD CRUSTACEA 



435 



Antenna with segment 2 greatly expanded, flagellum extending beyond antennule. 



Maxilla with exopod expanded and reaching behind maxillipede i, but without setae. 

 Maxillipede i with epipod. Maxillipedes 2 and 3 with rudimentary exopods, without setae. 

 Legs without coxal spines. Leg 5 with small bud representing exopod. Gills present. 



Pleopods and uropods large ; no spines dorsally on abdominal somite 6. 



It is naturally impossible to identify this Phyllosoma; but it is evidently closely 

 related to a form described by Stephensen (1923, p. 77) and referred by him to Themis 

 orientalis. The Discovery specimens do not seem to belong to the same species, as 

 Stephensen's figures show strong coxal spines on legs 1-3. Santucci (1926) has de- 

 scribed a larva of 30 mm., also from the Mediterranean, which appears to belong to the 

 same species as my specimens, and this larva he supposes also to belong to Themis 

 orientalis. 



There are great difficulties in accepting 

 such an identification. In the first place 

 T. oricjitalis is the only species of the genus 

 known, and it is confined to the Indo-Paci- 

 fic region, with the exception of a doubtful 

 record from the Adriatic, and one from Natal 

 (Von Bonde). It seems unlikely that it would 

 have been overlooked in the Atlantic if it is as 

 common as these larvae would show it to be. 

 It is also evident that there must be two 

 distinct species in the Mediterranean of the 

 genus to which these larvae belong. 



At the same time, our knowledge of the 

 distribution of adult Decapoda is not so 

 exhaustive that such an argument can have 

 much weight. 



If we knew only the Phyllosomas of Pali- 

 nurus and ScyUarus this Phyllosoma would 

 certainly be regarded as a Palinurid; but it 

 appears that the differences between these 

 two genera cannot be taken as valid for their 

 families. We have already seen that the absence 

 of an exopod from the maxillipedes is not confined to the Scyllaridae, and, if the Phyllo- 

 soma described below as Parribaciis} is in fact a Scyllarid, then a "Panulirid" form of 

 body may also be found in the Scyllaridae. The only character which seems to hold good 

 for separation of the families is the form of the antenna in the last stages, and in the 

 Phyllosoma in question there is a tendency to broadening of the base which indicates a 

 possible relation to the Scyllaridae. 



For these reasons I accept provisionally the reference of this form to Themis by 

 Stephensen and Santucci, but without conviction of its soundness. 



8-2 



Fig. 39. Themis sp. ?, Stage VII ?. St. 704. 



a. Antennae. b. Maxilla, etc. 



c. Abdomen. (/. End of leg 4. 



