182 Mr. T. n. Witliers o?? !<nme 



It would have been best, perhaps, to have fixed on one of 

 Darwin^'s specimens as the liolotype of the species, but in 

 view of the fact that all the specimens have been lost sight 

 of, I reluctantly fix on the scutum here figured (PL VII. 

 fig. 6) as the liolotype. 



Material. Only the scutum, tergum, and carina were 

 known to Darwin, but Dr. K. B. Nielsen has collected a 

 large number of valves comprising 74 carinse and rostra, 

 1.129 scuta (81 right and 48 lelt), 126 terga (64 right and 

 62 left), and 9 upper latera. Some of these which he 

 figured (1912) include a rostrum and an upper latus. 

 Among them are three peduncular plates, which, however, 

 show no signs of prominent transverse and longitudinal 

 ridges as one would expect them to if they belonged to such 

 a highly ornamented species as P. hriinnichi ; they agree 

 more in their ornament with the valves of the species SciUa- 

 lejjas dorsata, to which therefore I refer them. The valve 

 figured as a carinal latus is a rostral latus of S. dorsuta 

 (see p. 193). Dr. J. P. J. K-avn sent me from the Minera- 

 logical Museum of Copenhagen University the three pedun- 

 cular plates for examination, but, owing to the fact that the 

 *' carina! latus " has been lost, he sent other similar valves 

 determined by Dr. Nielsen, and these without doubt are 

 i-ostrai latera of S. dorsata. For the sjjecimens of P. briinnichi 

 figured in this paper 1 am indebted to Dr. Nielsen, as also 

 for 42 carint^ and rostra, 43 scuta, 91 terga, and 3 upper 

 latera. 



Although Dr. Nielsen records upwards of 300 valves, not 

 a single valve has been found that could be referred to a 

 lower whorl. 



Measurements. This species probably attained nearly to 

 the size of P. paronai. To judge from the figures given by 

 Dr. Nielsen^ the valves measured : — 



Lenotb. Breadth, 



mm. mm. 



Rostrum circa 10 5o 



Scutum „ 15"5 7'0 



Upper latus „ 6-0 1-5 



Ter^fuiu „ 15-0 8-0 



Carina „ 11-5 4-0 



The valves here figured (PI. YII. figs. 5-9), with the excep- 

 tion of the upper latus, are much smaller than the above. 

 Darwin (1851, p. 76) records a scutum as measuring 

 1"1 inches in length, which is much larger than that figured 

 by Dr. Nielsen. 



