Miscellaneous. 159 



The petrosal bone, completely covered externally by the qua- 

 dratum in Crocodilus, is i)artially exposed in Gavialis, and com- 

 jdctely so in Tcleosaurus and in Plcsiosaurus. 



Similar comparisons were pursued with respect to otlicr parts ; 

 and it is shown that in many respects the Tcleosuiiria bridge over the 

 gap between the long-necked EnaUosaurui and the existing Croco- 

 (lilia, — a conclusion not without interest, when the relations in time 

 of the two orders are considered. 



MISCELLANEOUS. 

 List o/" Diatomacese, ^c, found in Ceylon. By Dr. Kelaart. 



Amphora, sp. Gyrosigma tenuissimum. 



Eunotia amphioxys. lacustre. 



nimantidiuni gracile. Tryblionella, sp. 



arcus. Amphipleura, sp. 



Navicula firma. Atrikostonia falcatum. 



serians. 



lajvissima. 



bitVons. 



rhomboides. Vorticella nebulifera. 



Stauroneis gracilis. Carchesium polypinum. 



Pinnularia acuminata. Arcella enchelys. 



mesolepta. Trachelocerca biceps. 



viridis. Euglenia, sp. 



viridula. Chsetophyta ciunamomea, sp. n. 



— — gibba. Difflugia liosoma. 



Surirella panduriformis. Lioptomum. 



Nitzschia curvula. Trachelomonas gigas. 



ISIclosira distans. .—— laevis. 



Hanoptera semen. granulata. 



Three species of Nitzschia, nigra. 



probably new. 



On the Claws of the Spiders of the genus Mygale. By M. II. Lucas. 



M. Lucas has recently stated to the Academy of Sciences in Paris, 

 that the claws of the tarsi of the Mygale Blondii and M. nigra, 

 which are inserted above the tarsus, are very mobile, and that they 

 are exsertcd or retracted "by the animal at pleasure, somewhat in the 

 same way as those of the carnivorous mammals of the genus Felis. 

 lie has also observed that in these species the hooks of the man- 

 dibles are but sHghtly moveable, and that they are not developed to 

 the same extent as in many other spiders, such as those of the 

 genera Segestria, Epe'ira, Tegenaria, &c. 



During his stay in Algeria on two occasions, M. Lucas had the op- 

 portunity of examining several species of the genus Mggale, amongst 

 others M. barbara, gracilijjes, and africana, and in these he observed 

 that the claws were terminal and non-retractile. In these species 

 also the hooks of the mandibles are greatly developed, and serve 



