240 



only been known from a single and probably minute specimen, also obtained in 

 Shark Bay, and described by Dr. Thiele (I.e.). 



As I believe no previous description of this shell has appeared in any 

 English publication, I give the following free translation from the German : — 



"The colour of the shell is yellowish-brown with a few symmetrical dark 

 spots, the posterior portion of each valve is rose-red, the sutural laminae are 

 transparent, while the valves are fitted close together without any interspaces ; 

 shape of the median valves very little different from the others. Tegmentum 

 is somewhat arched, broader than long (probably this is due to its being an 

 extremely juvenile shell — Ashby), anteriorly fairly straight, posteriorly with a 

 distinctly produced beak; the posterior valve is, similarly, a little broader than 

 long, fairly flat, mucro overhangs the posterior margin ; the anterior valve and 

 lateral portion of others is distinctly sculptured with small warts. The 'tegmenta' 

 is similar to Acanthochites. Anterior valve 3 slits, others none. The girdle 

 banded brown, upper side clothed, not very closely, with larger and smaller, 

 round-ended, longitudinally-grooved, lime spicules, 140/xX17/i., 160 /xX 13 /a, and 

 60 /x, respectively. Shark Bay." (The spicules are highly polished, the longi- 

 tudinak grooving, more correctly scratching, can only be detected by use of a 

 fairly high power. I am indebted to Dr. Tiegs for the use of his microscope 

 in the matter of this determination. — Ashby.) 



Dr. J. Thiele, in his Introduction, explains that he mistook the little animal 

 for an Acanthochiton until he had disarticulated it ; this will account for his giving 

 no measurements. 



I conclude, from the figures he gives of the valves, that his specim,en was 

 a very juvenile shell, much less than the 7 mm. specimen collected at Carnarvon. 

 It is well to note that the valves of all very juvenile specimens of the members 

 of this genus are proportionally much broader than is the case in the adult ; 

 in this respect the valves of the juveniles of most species have a great similarity. 



Differences. — No doubt, for the reason stated above, Dr. Thiele gives no 

 figure of the complete shell and ignores one of its most distinguishing char- 

 acters, viz., that the spicules on the girdle are adpressed, or lying close to the 

 girdle, not erect, as is usual with other members of the genus Cryptoplax. I 

 have been able to detect the three forms of spicules as figured by Thiele (I.e.), 

 but the long, finger-like, slightly-flattened, round-ended ones (f. 15, I.e.) are by 

 far the most numerous, and differ from all other known Cryptoplax. 



The sculpture of the valves consists of rows of but slightly-raised, flat, or 

 squamose pustules, very similar to those on Acanthoehiton bednalli, and in this 

 respect different from any other known species. I give a photograph of the 

 whole shell and also of the valves. 



Cryptoplax hartmeyeri^ Thiele, 1911. 



PI. xix., fig. 1. 



(Fauna Sudwest Australiens, Polvplacophora, Thiele, 1911, pp. 405, 406, pi. vi., figs. 18-25; 

 Ashby, Trans. Roy. Soc. S. Austr., vol. xlv., p. 46, 1921 ; I.e., vol. xlvi., pp. 577, 578, 1922.) 



Dr. Thiele states that he had three specimens for examination, all from 

 Western Australia, two without any further data, and the other from Surf 

 Point, Shark Bay. He describes the general appearance of the large specimen, 

 40 mm. in length, as yellowish with dark brown, richly marbled, the valves 

 dark blackish-brown anteriorly, becoming lighter towards the posterior margin. 

 The four anterior valves touch one another, the four posterior are separated 

 by spaces that are greater than the length of the valves themselves. The figures 

 of both valves and spicules are from a smaller specimen, of which no measure- 

 ments or description, before disarticulation, are given. I conclude the 



