486 Observations on the 



species there is no connection, and apparently no indica- 

 tion that any ever existed. 



It seems more probable that as the ova were germinated 

 within the body, they found their exit through the central 

 summit aperture, and were conveyed along the small cen- 

 tral grooves of the pseudambulacral fields, before men- 

 tioned, beneath the plated integument, to the bases of the 

 tentacula, where they were developed and discharged, as 

 in the true crinoids. 



With the excoptiou of the union of each pair of the 

 so-called ovarian apertures, and their tubular prolongation, 

 as in this species, there is reason to believe that all the 

 known species of the group elliptici had essentially the 

 same summit structure, and which does not appear to be 

 analogous to that of the Jioreales in any of their known 

 modifications. The following observations, however, will 

 show that essentially the same summit structure was pos- 

 sessed by Pentremites slelliformis Owen and Shumard, 

 although it differs materially from all the elliptici, and 

 should be assigned to a group which would probably also 

 include P. sirius White. 



PENTREMITES STELLIFOKMIS Owen and Shumunl. 



Well-preserved specimens of this species show all the 

 summit apertures to be closed by minute polygonal plates, 

 unless we except a narrow slit on each side of the superior 

 end of the pseudambulacral fields, which are directed 

 downwards along their outer margins, and are somewhat 

 overlapped by what appears to be a greater development 

 of the poral pieces in these parts of the fields, where they 

 are considerably wider than at the extremities. These 

 slits may have served the same purpose as the ovarian or 

 siphonal apertures in other Pentremites. 



The anal aperture is completely closed by a disk of 

 minute polygonal plates, which in the specimens exam- 



