Loven — On Leskia Mirabilis. 181 



face of attachment is of a very variable form and extension in diffe- 

 rent specimens, — round and but little excavated in some, oblong and 

 deep in others, — depending upon the nature of the object to which 

 it adhered. On the point opposite to this basal surface lies the 

 apex with the ambulacral apparatus. In the middle a somewhat 

 deepened area d, through which five delicate but distinct ambulacral 

 furrows pass towards five arms, whose bases form a circle, which 

 however is broken at i, one-fifth of its circumference. Where 

 the furrows reach the arms, they will be seen to pass into an oblong 

 hole e, which is the lumen of the broken furrow of the lost arm ; 

 in every remaining arm-base you will see an indication of the 

 branching of the arms and of the central channels of the branches. 

 Close up to the ambulacral circle lies the '' pyramid" or mouth a, 

 closed by its five valves of unequal dimensions, two of them are 

 emarginate on one side in order to give space to the two adjoining 

 outermost arms, which are less than the others, and, as it were, 

 crippled, the right by its vicinity to an oral valve, the left by an 

 apparatus h, that cannot be interpreted otherwise than as an ex- 

 ternal genital organ. When it is tolerably well preserved, it is 

 conical, with a rounded apex, without any terminal aperture ; for 

 vestiges of valves I have sought in vain, but in two specimens I 

 found the two pores indicated in the figure. From this organ a 

 ridge c runs towards the next arm, suggesting the idea of the possi- 

 ble existence of a '' madreporite." The centre of the brachial appa- 

 ratus forms with the genital organ, and the oral orifice a compressed 

 but only slightly inequilateral triangle. In EchinosphcBrites auran- 

 tium the relative position of these parts is the same, but the triangle, 

 which they form with each other, is much larger, longer, and more 

 inequilateral, because the distances are greater, especially that of the 

 mouth from the ambulacral apparatus, which is correctly described 

 and delineated by Volborth and Joh. MuUer. Close to this is seen 

 the other " orifice," viz., the external genital organ. All specimens 

 that I have examined have this so-termed "orifice" in such a con- 

 dition that it most likely is the remnant of a prominent broken part, 

 and it must be assumed that in this species also it had a conical 

 form, but remained mainly in the surrounding stone-matrix. Vol- 

 borth's figm-e (Ueber die Eussischen Sphasroniten, x. ix. f. 9) appears 

 to be correct, but gives no complete evidence as to the presence of 

 the three valves." That the "pyramid," which in Leskia is the 

 armature and covering of the mouth, is the same thing in Cystidea, 

 is now quite certain ; in the last-named group it was, doubtless, also 

 the vent. The mouth does not lie where J. Miiller and Volborth 

 sought for it, viz., in the centre of the ambulacral furrows ; and the 

 organ, interpreted as the vent by Volborth and von Buch, is more 

 correctly regarded as an external sexual organ." 



It is not my intention to criticise the various interpretations 

 of the morphology of Cystidea given by different authors, or 

 to trespass on the space here allowed me by a detailed examina- 

 tion of aU the questions entangled with them. But should I 

 venture to express any humble opinion of my own on this important 



