1880.] MR. F. J. BELL ON A NEW GENUS OF ECUINOIDS. 4!) 



from Echinoneus it is distinguished by the fact that the paired pores 

 do not extend from apex to actiuostome ; with the remainder of the 

 Cassidulids, however, it has considerable affinity. In several points 

 it presents resemblances to Rhynchopygus ; but this curious genus is 

 sharply distinguished by the position of its anus ; Neolampas has but 

 a double row of simple pores ' in each ambulacral area ; Echinolampas 

 has one of its two paired rows of pores considerably shorter than the 

 other in each ambulacrum ; and Conodypeus, with which Valceolampas 

 presents the greatest affinity, differs from it in having retained the 

 primitive position of the mouth, and in nevertheless having obtained 

 large bourrelets, as well as having the pairs of pores united by grooves ^ 

 Conodypeus also has the apical system specially modified into a pro- 

 jecting button-like piece, and has the ocular plates very small. 



On the whole, then, Palceolampas seems still to retain in its 

 organization points of structure which show that it either diverged 

 from the Cassidulid stem rather earlier than Conodypeus, or that 

 it stands in the direct line which connects this genus, first seen in 

 the Cretaceous epoch, with a still more generalized ancestor. As it 

 presents, therefore, a grade in development, we can only justly 

 recognize the value of the characters which it presents by forming 

 for it a special genus ; and the name which is proposed seems to be 

 one that it is justified by' the characteristics herein detailed. 



Returning to the question with which we started, we find, I think, 

 that the existence of an intermediate form of this kind, continued on 

 for so long a period of the world's history, as it is almost certain it 

 has been, must make us very careful as to accepting any statements 

 which seem to throw discredit on that principle of most modern 

 evolutionists, which ascribes the origin of species to the effects of 

 variations, not always seen by the unobservant eye. And while the 

 explanation suggested as to the instability of certain combinations 

 of anatomical characters may throw light on some of our difficulties, 

 it is hardly yet time for us to cease giving the proper weight to our 

 limited opportunities, and the imperfections of the records of the 

 past, or, on the other hand, to forget how species best adapted for 

 investigation are not always those that have most completely retained 

 an uneffaced record of their past changes. 



DESCEIPTION OF PLATE IV. 

 Fig. 1. Palmolampas crassa : view of the abiictiiial surface, to show the dis- 

 position of the rows of pores, and the character of the plates of the 

 coi'ona. Natural size. 



2. P. crassa : view of actinal surface, to show the characters of the bour- 



relets and phyllodes iu the distribution of the ambulacral pores. Nat. 

 size. 



3. P. crassa : profile view. Nat. size. 



4. Abactiual system, enlarged, to show the size of the ocular and genital 



plates, the characters of the ocular pores, and the position of tlie 

 madreporic plate. 



' See Wyville Thomson, ' Phil. Trans.' vol. clxiv. pt. 2, p. 745. 

 ^ In C. leskii the aetinoslome is some way in front of the centie; but it is a 

 question whether this species truly belongs to the genus CunocU/pcus. 

 Proc. Zool. Soc— 1880, No. IV. ' 4 



