3o6 DISCOVERY REPORTS 



GROUP I 

 With epipods and with exopod on leg 5 



Group I A 

 Dorsal spines unpaired 

 With the exception of species B.R. II this group may be regarded as reasonably 

 uniform, and in all probability belonging to the Axiidae. Species B.R. II, with its short 

 rostrum, reduced exopod on leg 5 and telson of Callianassid form, can only be included 

 here by reason of its possession of epipods and four pairs of pleopods. On the other 

 hand, the absence of dorsal spines on somites 2 and 3 seems definitely to exclude it 

 from ColUanossa type I. Its position remains problematical. A very similar form has 

 been described by me (1924, p. 145). In this species pleurobranchs were seen on legs 

 2-4, and it was suggested that it might belong to Iconaxiopsis . It may be possible to 

 distinguish three types of Axiid larvae : 



(i) Telson of "A" type. Exopod of leg 5 long. 



(2) Telson of "C. I" type. This exopod vestigial. 



(3) Telson of "C. 11" type. This exopod vestigial. Example: A. stirhymchus. 



It may be that types (2) and (3) are also distinguished by absence of some of the dorsal 

 abdominal spines. 



Thalassinid D. I (Fig. 6) 



Oodeopus intermedius. Bate, 1888, pi. 143, fig. i. 

 "Atlantis" St. 1121. 35° 53' N, 62° 45' W. 



Rostrum 4-9 mm. ; body 10-9 mm. 



Rostrum very long, narrow; basal part hollowed above but with median dorsal 

 ridge, serrated; distal part slender, smooth. Carapace with a few teeth on anterior 

 ventral margin. Somite 2 of abdomen with large dorsal spine, shorter than somite 3 

 and not greatly larger than spines of somites 3-5. Pleura of somites 2-4 with sharp 

 ventral point. Anal spine large. 



Telson parallel-sided, nearly four times as long as wide; with four widely spaced 

 lateral spines, anterior spine about middle; distal part produced and tapering to the 

 large median spine, with nine small spines on either side. Spine formula 13, i, 13. 



Eye oval, black. Antenna: basis with very long outer spine and small inner spine; 

 scale with plumose seta on under side near base. Mandible with unsegmented palp. 

 Maxillule with palp slender, unsegmented, with eight setae. Maxilla with palp slender 

 of three segments. 



Maxillipede i with endopod of four segments, with outer seta on segment i. This 

 seta is, in the forms here dealt with, generally on the anterior face and turned inwards, 

 so that it is invisible from the posterior face. It is probably always present, but may be 

 overlooked. 



