718 MR. s. KEMP ON DECAPOD [June 15, 



apical system may have been resorbed, as they should have 

 existed at the adapical extremities of the truncated ambulacra in 

 the early and normal phase of the animal's existence. There is 

 no sign of their having been carried down to remain in their 

 terminal position at the ends of the ambulacra. 



There is a small hole in the middle of interambulacrum 2 

 which does not look like a mere chance puncture inflicted after 

 the death of the animal, as it seems to have been partly healed 

 up by a fresh deposition of calcite from within. The hole may 

 be the result of the activity of some boring parasite, but whether 

 such an agent could cause the remarkable irregularities that 

 exist in the test seems very doubtful. 



The following are a few important measurements of the test : — 



mm. 



Length (ant. rad, to post, interrad.) 36 



Breadth (at right angles to above) 31 



Height (including apical system) 30 



Ambitus 115 



Diameter of peristome 10 



Leng-th of apical system 7*75 



Breadth of apical system 5 



From rad. Ill to nearest point of apical system . 14*5 



.. ^» V ,, ,1 ,5 1) 1, 5, ^^ 



5. The Decapods o£ the Genus Gennadas collected by 

 H.M.S. ' Challenger/ By Stanley Kemp, B.A.* 



[Received Juae 7, 1909.] 



(Plates LXXIII.-LXXY.t) 



In 1881 J, Spence Bate established the genus Gennadas for the 

 reception of certain abyssal Penjeidfe found by the ' Challenger ' 

 Expedition. He recognized two species, G. 2Xirvus and G. inter- 

 onedius, but his descriptions and figures, viewed from the stand- 

 point of our present knowledge, are hopelessly inadequate. 

 Since 1888, when the full Report on the ' Challenger' Crustacea 

 Macrura appeared, several authors have recorded Gennadas parvus, 

 but owing to the imperfections in the original description it 

 may be doubted Avhether much reliance can be placed on their 

 determinations. 



Only quite recently has any good basis been formed for future 

 work. Bouvier, in 1906 §, outlined a scheme for the identification 

 of six Atlantic species and emphasized the value of several 

 characters as specific determinants ; by means of these species he 



* Communicated by Dr. W. T. Calman, F.Z.S. 

 t For explanation of the Plates see pp. 729 & 730. 

 1 Ann. Mag. Nat. Hist. Sept. 1881, p. 91. 

 § Bull. Mus. Oceanog. Monaco, 80, 1906. 



