BRACHIOPODA. 183 



SLPPLEJNtEXTARY >;OTE ON THE GENUS KUTORGINA. 



Some interesting observations which bear upon the phylogenetic rehitions of 

 this obscure genus, have recently been made by Mr. G. F. Matthew, in a paper 

 entitled " Canadian Organisms in Acadia," published in the Transactions of the 

 Royal Society of Canada, article xii, p. 135. 1890. The author has described 

 and illustrated the development of his species, Obolus pulcher (see Plate IV k, 

 fig. 22), and though it may not be proven that this form can be safely included 

 within the genus Obolus, it is distinctly oboloid. These observations are based 

 upon adult shells which retain evidence of differential stages of shell-growth 

 with sufficient distinctness to allow of the following subdivision : 



" (1) Embryonic. Formation of the embryonic shell. 



'' (2) Larval. Lengthening of the hinge-line and acquisition of mantle 



margins. 

 " (o) Adolescent. Fixation of the hinge-line, otherwise as the last, except 



the radular ornament jjecomes irregular. 

 " (4) Adult. Absence of radular ornamentation on the valve and great 



expanse of the mantle margin." 



In the earliest stages represented (plate viii, figs. 1 a-e, brachial valve, figs. 2 

 a-d, pedicle-valve), the hinge is straight and long, making the greatest diameter 

 of the shell, the umbo of the pedicle-valve is elevated and the cardinal area 

 erect and with a triangular pedicle-aperture. The resemblance to Kutorgina 

 in the growth-stage is at once striking, and it mav serve to indicate the sub- 

 ordinate value of this genus in its relation to the oboloid stock. 



