124 PKOCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



seen no similar tail-valve yet in any other Chiton. The upward 

 curve of the tail-valve of Plaxipltora [Fremlleya) egregia (H. & A. 

 Adams) is recalled, but this instance much exaggerates it. Besides, 

 in that case there is no convex lateral area, which is clearly shown in 

 this. Upon dissection the tail-valve was found to possess, instead 

 of an insertion-plate, simply a callused ridge showing faint striations. 

 In his Revision des Systems der Chitonen (Chun's Zoologica, Heft Ivi), 

 Thiele (p. 34) introduced for a Mauritian shell Craspedochiton 

 i^Thaumastochiton, n.subgen.) mobiiisi, n.sp. 



Beautiful figures are given on Taf. iv, figs. 36-48, and the Amirantes 

 shell certainly falls into the sub-genus Thaumastochiton, though it 

 may specifically differ from Thiele's Mauritian form. The tail-valve 

 in the latter, judging from Thiele's figures, does not show such 

 an upcurved mucro, nor possess such a well-defined, convex, 

 lateral area. 



As the Amirantes would geographically fall into the Mauritius 

 area, and further, as only one specimen is available, I would minimize 

 the observed differences and record this shell under Thiele's species- 

 name. On account of the interest this sub-generic form must have to 

 all Chiton students, I have brought forward this alteration, and would 

 note the rejection of laqueatus, Sow., from the Amirantes fauna. 

 Thiele (p. 116) under Thaumastochiton made a footnote " Dahin 

 gehort wahrscheiulich ' Onithochiton'' isipingoe^isis, Sykes (P. Malac. 

 Soc. London, vol. iv, p. 259) von Sud-Afrika". This induced the 

 examination of Sykes' species, the type of which is preserved in the 

 British Museum. It was obviously no Onithochiton, judging from 

 the description alone, and was as certainly a Craspedocliitonoid shell. 

 Thiele's suggestion proved correct, since, though ' 0. ' isipingoensis, 

 Sykes, differed altogether in sculpture from the Amirantes shell, the 

 tail-valve agreed minutely in structural characters. Sykes' description 

 of the tail-valve is here reproduced: "Posterior valve similarly 

 sculptured, but having a dorsal area ; it is concave above and the 

 mucro is posterior. , . . The insertion plate of the posterior valve is 

 flattened behind, and appears to be without any slit, the tegmentum 

 overhanging, and the valve being obtusely beaked behind." 



Chiton petasus, Ileeve. 



This species is described in the Proc. Zool. Soc, 1847, p. 25, 

 and figured in the Conch. Icon. Chiton, and also in the Zoology of the 

 Samarang. In the Man. Conch., vol. xiv, p. 311, Pilsbry placed 

 tliis species in the genus Placiphorella, with the note " Eeferred to 

 this genus on account of the peculiar girdle ". At that time the genus 

 Craspedochiton was imperfectly known, and consequently it was 

 a forgivable error to overlook the undoubted relationship of Reeve's 

 species to that genus. However, quite recently Nierstrasz, deter- 

 mining the Chitons of the Siboga Expedition (p. 43, 1905), has 

 introduced a new species of Craspedochiton with the name tesselattis, 

 which, coming from the same locality, seems to be the long-lost 

 Reevean species. It should be observed that in the same paper 



