I. '08. 65 



series along the inferior margin of the carapace and single un- 

 paired photophores on the inferior aspect of the sixth somite 

 and on the dorsal surface of the telson. 



The table here given will show the number and positions of 

 all the luminous organs present in a selected series of speci- 

 mens ranging in size from larvae up to the adult. 



The other more interesting features in the post-larval his- 

 tory are the development of the rostrum, eyes and branchiae. 



The rostrum remains perfectly straight up to about 20-25 

 mm., and after this is almost always distally ascendant. It 

 attains its greatest proportional length in examples of 35-40 

 mm., when it is often rather more than twice the length of 

 the carapace. 



The eyes, as Coutiere (loc. cit.) has shown, reach their 

 maximum size in proportion to the body area of the specimen 

 at a length of about 15 mm. 



As has been already stated, the branchiae are very rudi- 

 mentary in the larval stage, the buds of five pleurobranchs 

 being alone present. Their development in the earliest post- 

 larval stages has already been dealt with by Coutiere (loc. cit. 

 fig. 2 d). In the specimens of 12'7 mm. they are exactly as he 

 has described, i.e. five pleurobranchs, which are only pinnate 

 basally, corresponding to the five pereiopods ; two buds, repre- 

 senting arthrobranchs, over the third maxillipedes and an 

 arthrobranchial and an epipodal bud at the bases of the first 

 four pereiopods. Eudimentary epipods are also present on 

 the first and second maxillipedes. The arthrobranchiae seem 

 to develop slowly after this, for in a specimen of 27 mm., 

 although they are completely pinnate, they are still very small, 

 and have only grown a very short way up between the large 

 fully-formed pleurobranchs. 



The mandibular palp is fully developed in an example of 

 only 15 mm. 



General distribution. — Four isolated specimens have been 

 found in the West Atlantic between New York and the West 

 Indies (Milne-Edwards, Faxon and Smith). In the N.E. 

 Atlantic the species is know^n from near the Azores (Coutiere), 

 from the Bay of Biscay (Kemp), from the mouth of the Eng- 

 lish Channel and oif the Brittany coast (Hansen), w^hile a 

 single example has been found S. of Iceland in Lat. 62° 47' N. 

 (Hansen). A solitary individual has been recorded from the 

 Pacific, near the Haw^aiian Is. (Rathbun). 



Several of the specimens examined were caught by the 

 Danish Fishery steamer Thor at the following localities : — 



31/5/'06.— 51° 4' N., ir 39' W. Midwater trawl, 0-437 

 fathoms — Three, 30-71 mm. 



7/6/'06.— 48° 29' N., 14° 15' W. Midwater trawl, 0-940 

 fathomis — Two, 38 and 66 mm, 



5/6/'06,— 49° 17' N., 14° 3' W. Midwater trawl, 0-164 

 fathoms — Four, 28-42 mm. 



R 



