338 DISCOVERY REPORTS 



Mandible asymmetrical, that on left sickle-shaped ; right mandible with cutting part 

 pointed and molar part forked. Paragnath on left produced into a very long curved 

 spine. Maxillule with palp unsegmented; laciniae widely separated. Maxilla with 

 four well developed inner lobes ; palp minute ; exopod large, with slender proximal part. 

 Maxillipedes i and 2 with endopods of four segments, without outer setae on seg- 

 ments 1-3, inner setae without coarse feathering; coxa very small and basis elongated. 

 Maxillipede 3 and legs with rudimentary endopods seated low down on basis ; exopods 

 on legs 1-4, leg i chelate, leg 2 not chelate. 



Pleopods very small, on somites 2-5. 



A precisely similar form, in the same stage, was taken at Barrier Reef St. 49, and 

 a specimen in stage I at Samoa. 



Stage I. Length 2-4 mm. 



Rostrum and general form as in later stage. Telson slightly hollowed behind, with 

 outer spine, reduced spine 2 and a formula of 7 + 7. 



Antennule unsegmented, without spine-like process seen in Jaxea. Antenna : exopod 

 with ten setae and small apical spine ; endopod long and stout, with three apical setae ; 

 basis with one small ventral spine. Maxillipedes i and 2 functional; maxillipede 3 

 and leg i rudimentary. 



This very interesting new form has the same peculiar form of mandibles and maxillules 

 as Jaxea and Naiishonia and must certainly belong to a closely allied genus ; but it differs 

 from both in having no elongation of the head region and in the presence of an exopod 

 on leg 4, and of a small median spine on the telson. The general form so closely resembles 

 that of Upogebia that its real position was not realized until it was examined in detail. 



The occurrence of larvae apparently specifically identical at points so widely separated 

 as the western Atlantic and Samoa is remarkable, but a similar wide distribution has 

 been noted above for certain Axiid-Callianassid larvae. The known distribution of 

 adult Decapods is generally much more restricted, but Stenopus hispidus is known to 

 range from the West Indies to Hawaii, and Calocaris macandreae has been recorded 

 from Ceylon and New Zealand. 



Menon (1933) has described as a member of the Upogebiinae a larva which is 

 remarkably like the one dealt with here. The general form is the same, and it has the 

 lateral spines on somite 5, but no pleural spines on somites 2-4. The telson is exactly 

 the same, and the maxillule and maxilla very much alike ; but it lacks the sickle-shaped 

 left mandible and the exopod on leg 4. The presence of epipods on the legs and of an 

 appendix interna on the pleopods in the post-larval stage makes reference to the 

 Upogebiidae impossible, and its position must remain in doubt. The combination of 

 characters given would exclude it from any of the families of Thalassinidea at present 

 known. 



