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Show 48 MR. F.J.BELLONANEWGENUSOFECHINOIDS. [Feb. 3, The actinal surface of the test is completely plane; the ab^tmal sur-face is obtusely pyramidal, the area around the ocular and genital^pores being flattened out to form what may be called an apical P^teau I propose to call the genus to which this specimen belongs Palceolampas, and to define it thus :- A petalostichous Echinid in which the completely parallel ambulacral pores remain 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, lubercles 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. P A L C E O L A M P A S 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 specimen described:- millim. Greatest length 102 Greatest width 96 Greatest height 4o 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 I „ „ (leftside)........ 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 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 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 semitce |