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BISCAYAN PLANKTON. 



Part XI.— DECAPODA. 



By Stanley W. Kemp, B.A. 

 [Communicated by Dr. G. Herbert Fowler, F.L.S.) 



(Plates 14 & 15.) 



Ui LI B R A R Y!: 



Read 7th ilareh, 1907. 



So will be readily understood, the large majority of the Decapoda collected by Dr. Powler 

 in the Bay of Biscay are larval forms. 



Tow-nets, unless of exceptional size, are but ill adapted for the capture of free- 

 swimming Macrura, many of which are powerful swimmers and easily avoid capture 

 in small nets. Nevertheless, iive species are represented by specimens which have 

 attained adult characters ; they are — Amalopenceus elegans, Smith, Sergestes arctlciis, 

 Kr., AcantheiJhyra purpurea, A. M.-Edw., Acanthephy7^a{St/stellaspis) debilis,A.. M.-Edw., 

 and Hynienodoni glacialis, Buchholz. The last named is represented only by macerated 

 fragments, and its identification therefore cannot be regarded as absolutely satisfactory. 

 So far as is at present known, only a small percentage of Macrura are pelagic, so that 

 tbe five species mentioned above probably represent about one-half of the free-swimming 

 forms which might occur in the district vmder observation. 



The chief interest of the collection ce'ntres in the fine series of larval Acanthephyra 

 purpw^ea. The later stages in the development of this form have been determined by 

 Coutiere, and the material before me enables me to substantiate his sus-iyestion that the 

 species leaves the e^^ in the form of a zoiea. A comparison of the development of 

 this species with that of A. debilis renders this feature noteworthy enough : A. debilis 

 has much larger eggs than A. purimrea, ViV\(\. Coutiere states that the young leave the 

 egg in a post-larval condition *. 



This series of young A. x>itTpurea comprises the vast majority of the larvae in the 

 collection, but in addition there are a few interesting Hippolytida? closely allied to 

 Spence Bate's larval genus Caricyphus. Only three larval Anomura arc present ; and 

 Brachyura are represented by a few metazoteae and megalopse. Numerous examples of 

 all these larvae occur in our extensive material from the west coast of Ireland, and it 

 seems best to defer any detailed notice of the few specimens taken in the Bay of Biscay 

 until such time as I can deal with this large collection, which will probably enable many 

 of them to be connected with well-known adult forms. 



* This statement is, however, incorrect : see note on p. 214. 

 SECOND SERIES. — ZOOLOGY, VOL. X. 



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