48 MR. F. J. BELL ON A NEW GENUS OF ECHINOIDS. [Feb. 3, 



The actinal surface of the test is completely plane ; the abactinal sur- 

 face is obtusely pyramidal, the area around the ocular and genital pores 

 being flattened out to form what may be called an apical plateau. 



I propose to call the genus to which this specimen belongs 

 Palaolampas, and to define it thus : — 



A petalostichous Echinid in which the completely parallel ambu- 

 lacral pores remaia paired as far as the ambitus, and in which the 

 tendency to the shortening of one of the two sets is only very slightly 

 indicated in the antero-lateral pair ; the outer row of each pair of 

 pores is regularly distributed from the apical area to the actinostome. 

 Bourrelets feebly developed. Anus elongated transversely, infra- 

 marginal. Four genital pores ; ocular pores large. Tubercles all 

 primary, and equally distributed over the test. Test not very high. 

 Apical system and actinostome a little in front of the true centre of 

 the test. 



Pal^olampas crassa, nov. sp. (Plate IV.) 



Test very thick, with a flattened apical plateau, pores of phyllodes 

 not very regularly arranged ; anus looks almost as much backwards 

 as downwards ; in the antero-lateral ambulacra the anterior row of 

 pores shorter by three or four pairs than the posterior. 



Hab. ? India. 



The following are the more important measurements of the speci- 

 men described : — 



millim. 



Greatest length 1 02 



Greatest width 96 



Greatest height 46 



Length of anterior ambulacra 46 



Length of antero-lateral ambulacra (right side) 46:49 



(left side) 44 : 50 



Length of postero-lateral ambulacra (right ride) 62 



„ „ „ (left side) .... 63 



Distance from anterior edge of actinostome to edge of test 44 

 Distance from posterior edge of actinostome to posterior 



edge of test 50 



Greatest antero-posterior axis of actinostome 8 



Greatest transverse axis of actinostome 12 



Greatest transverse axis of anus 12 



Greatest antero-posterior axis of anus " A' 



Greatest antero-posterior axis of madreporic plate .... 7 



Greatest transverse axis of madreporic plate 7 



Greatest intraambulacral width (from inner pores) .... 10 



„ „ (from outer pores) .... 14' 5 



>i 



It now remains only to discuss the systematic position of this 

 interesting form. It obviously falls into the edentulous division of 

 the Petalosticha, or into the Petalosticha as defined and limited by 

 Alex. Agassiz. From the highly modified Spatangidae it is at once 

 distinguished by the absence of the plastron and of the semitse ; 



