456 Mr. G. B. Sowerby on Pentatrematites 
Art. LXII. On Pentatrematites orbicularis, acuta, and 
pentangularis. By G. B. Sowrersy, F.L.S., &c. 
In two former papers* I have described what I suppose to constitute 
eight distinct species of Pentatrematites. Three others having since been 
discovered by Mr. Gilbertson, he was induced by the expressed wish of 
some friends to science, to forward descriptions of and observations on 
them for publication in this Journal. By some unaccountable accident 
his paper has been mislaid, and it becomes necessary, in order to 
complete the subject as fully as possible, that JI should here add the 
characters of these three species. And I beg permission to subjoin a 
note or two which I find accompanying the drawings with which my 
brother will illustrate this and the last-cited paper. 
The first of these notes is as follows, ‘‘ the ambulacra are composed 
“© of two rows of bones placed in two furrows by the sides of an angular 
** ridge, and so articulated as to leave a pore between each; these bones 
** often fall off: the pores continue into the edge of the furrows.” 
The other note is ‘* there were two specimens of P. elliptica showing 
** pores for respiration in the ambulacra; these pores are connected with 
‘* passages that lead to what are called the ovaries.” 
: PENTATREMATITES ORBICULARIS. 
P, globosa, feré circularis. Scapulares mediocres, usque ad dimidium 
attingentes, emarginationis interscapularis angulo obtusissimo. 
Interscapulares majores. Ambulacra linearia, angusta, ad basin 
prominula. 
Tas, SuprL, XXXIII, fig. 5. 
PENTATREMATITES ACUTA. 
P, pyriformis, pentagonalis, superné lata, infra attenuata, Ambulacra 
brevia, lata, angulis superné conspicuis. 
* Vol. II, p. 313, and Vol. IV., p. 89. 
