383 



type specimens of 0. pritchardi, lent to me with great 

 cordiality by Prof. W. Howchin. 



I am quite unable to separate the above cephalons ; I 

 believe them to represent one and the same species. I do not 

 quite follow Mr. Walcott in his reference of ' '' Dolichometopus 

 tatei" to the genus Redlichia. The fixed cheeks are so differ- 

 ently shaped, the direction of the ocular ridges so dissimilar, 

 that the courses of the facial sutures must have been quite 

 unlike those of the Indian genus. At the same time I am 

 by no means satisfied by merely placing these partial cephalons 

 in Ptychoparia . 



On looking round for a similar structure to that I have 

 here termed a "bridge," uniting the anterior end of the 

 glabella to the limb border, the genera Alokistocare^ 1 ) and 

 A crocephalites ( 38 > obtrude themselves. In the former, "a low 

 rounded boss occurs in front of the glabella, that usually ex- 

 tends across the frontal limb (area) on to the frontal rim so 

 as to interrupt the furrow delimiting the two"; the boss 

 appears to be variable in development according to species. 

 In the latter of the two foregoing genera this bridge is referred 

 to as "a knob-shaped elevation," but in a cephalon placed 

 in this genus with reservation by Mr. Walcott, the glabella 

 is connected with the limb by a well-defined narrow median 

 ridge . 



Loc. — Curramulka (or Parara[?]), Yorke Peninsula, 

 South Australia (Tate). 



Hot. — Parara Limestone, Lower Cambrian (Tate); 

 Upper Cambrian (Howchin); Cambrian (Etheridge). 



Ptychoparia ( ?) subsagittatus, Tate. 



PI. xxxix., figs. 4 and 5. 



Microdiscus subsagittatus, Tate: Trans. Rov. Soc. S. Austr., 

 xv., pt. 2, 1892, p. 187, pi. ii., fig. 12. 



Obs. — Tate's "Microdiscus subsagittatus" has no con- 

 nection with the genus of that name. I have before me 

 Tate's two specimens and two others lent to me by Prof. 

 Howchin. 



The resemblance between Tate's examples of his "Ole?i- 

 ellus pritchardi" and "Microdiscus subsagittatus" is remark- 

 able. In neither of the two type specimens of the latter is 

 the true outline of the cephalon shown, but the fixed cheeks 

 are slightly more cornute that in "0. pritchardi," the ocular 

 ridges somewhat more sigmoidal. What, however, is of more 



. (37) Walcott: Smithsonian Miscel. Collns., 64, No. 3, 1916, 

 p. 182. 



(38) Walcott: Ibid, p. 174. 



