216 



MONOGRAPH ON THE AUSTRALIAN LEPIDOPLEURIDAE ORDER 

 POLYPLACOPHORA, WITH A DESCRIPTION OF A NEW SPECIES. 



By Edwin Ashby, F.L.S., M.B.O.U. 



Plates XVI. to XIX. 



[Read May 10, 1923.] 



Fam. Lepidopleuridae, Pilsbry. 

 Genus Lepidopleurus, Risso, 1826. 



Of the four genera included by Pilsbry under the family name, two only 

 are foinid in Australian waters (Man. Con., vol. xiv., pp, 1, 2), and one of these, 

 Choriplax—Microplax, of Adams and Angas, has been shown by the writer 

 (Trans. Roy. Soc. S. Austr., vol. xlv., 1921, Ashby) to belong to a very different 

 family, that of the Acanthochitidae. 



Thus the known Australian representatives of this family are all confined 

 to the genus Lcpidopleurus, Risso. 



Genus Lepidopleurus, Risso, 1826. 



Pilsbry (I.e.) gives the following characters : "Insertion plates absent. Girdle 

 with minute, gravelly, smooth, or striated scales. Type, L. ca jet anus, Poli." 

 He also adopts and publishes a description of Carpenter's section Dcshaycsiclla, 

 Carp.. 1878: "Girdle having delicate spines and chaffy scales. Valves curved 

 and beaked, sutural plates and sinus as in LcpidoeJiiton. Type, L. cnrvatus, 

 Cpr." 



Thiele (in Chun's Zoologica Heft., Ivi., Rev. des Systems der Chitonen, 

 pt. 1, p. 14, 1909) proposes a subgenus, Paraehiton, with L. acuminatus, Thiele, 

 from Duke of York Island as type. 



Iredale, in paper on Chiton Fauna of the Kermadec Islands (Proc. Mai. 

 Soc, vol. xi., pt. 1, March, 1914), places his new species L. mestayerae under 

 Thiele's subgenus, suggesting that it be elevated to full generic rank, and pro- 

 poses another subgenus, Tercnoehiton, Iredale, with L. tropicalis, Iredale, as 

 type, and suggests that all the small Australian representatives of the genus 

 Lepidopleiirus be referred to this subgenus. 



Iredale and May, in Misnamed Tasmanian Chitons (Proc. Mai. Soc, pts. 2 

 and 3, November, 1916, pp. 98, 99), discuss Australian representatives of this 

 genus from Tasmania and South Australia, reaching no definite conclusion, but 

 stating: "However, all those we have examined seem to fall into Paraehiton, 

 since the girdle appears to be covered with slender, glassy spikes." Personally, 

 for the present, I am disinclined to adopt any of the suggested subgenera, but 

 would point out that Carpenter's and Pilsbry's section Deshaycsiella, which 

 was published by Pilsbry (I.e.), seems to exhibit the characters of some of the 

 Australian species and antedates Thiele's subgenus Paraehiton. I find that the 

 spicules, even more than the scales, in members of this genus, become easily 

 detached, so much so that species that have been supposed to be bare of spicules 

 are found on the examination of fresh, well-preserved specimens to have them 

 present. I have already, in a previous paper, expressed doubts as to the wisdom 

 of dividing this genus into subgenera on such a character. 



My thanks are due to Mr. W. L. May, of Tasmania, and Dr. W. G. Torr, 

 of this State, for the loan of much material without which the production of 

 this paper would have been impossible. 



