1873.] J. Wood-Mason^O?^ BliopalorliyncTius Krdi/eri. 171 



omnino dejlexo ; hasi circa iimhilicum rotundate subangulata, similariter 

 costulata, costulis usqiie ad periplieriam extensis ; apcrtura fere horizon- 

 taliter deflexa^ transversim rotundate elliptica, margins dilatato fere undique 

 libero, ad anguluon umlilici angustissime adnata^ circwnidata. Diam. viaj. 

 13*3, d. mill. 11'2, altitudo totius tested 6 ; altitudo apert. cum peristomate 

 5"5, ejusdem latitudo G'8 on.m. 



Hal). — BeJgaom, India occidentali. 



The present species has to be placed m close proximity to T. crassicostata, 

 and is as closely allied to it as this is to T. fallaciosa. It differs very marked- 

 ly from crassicostata by its more distinctly orbicular and depressedly 

 planorboid shape, by a well marked, smoother and thinner, peripherical keel 

 on the last whorl, by a more inflated and towards the middle more contracted 

 base, it being angular round the umbilicus, and by a considerably more 

 deflected aperture. 



In a former paper*' I expressed a doubt about S. fallaciosa, ruginosa, 

 and nilgliirica belonging to the genus Trachia, as originally proposed by 

 Albers. I observe, however, in well preserved specimens, that all of them 

 possess the peculiar granular structure which is so characteristic of TracTiia. 

 T. crassicostata and Footei must now be added to the list of these closely 

 allied Western Indian species. 



On EnoPALORHTNCHiJS Keoteei, a new genus and species of Ptcno- 

 GONiDA, — hy James Wood-Mason, of Queen's College, Oxford. 

 [Received and read May 7th, 1873.] 

 (With plate XIII.) 

 Much difference of opinion has prevailed with regard to the systematic 

 position of the Bycnogonida, as to whether they should be classed with the 

 Crustacea or with the Arachnida. By one set of naturalists, including 

 Johnston, Milne-Edwards, Quatrefages, Kroyer, and Dana, they have been 

 placed with the Crustacea ; by another — including Latreille, Erichson, Ger- 

 staecker and Huxley who separates them, as well as the Tardigrada and 

 Pentastomida, from the typical Arachnida (Spiders, Mites and Ticks) as an 

 aberrant order, — with the Arachnida. Dr. Anton Dohrnf who has recently 

 studied the embryology of these animals finds that they are in no way 

 related to the Arachnida, that they resemble the Crustacea in having a 

 naupliiform first developmental stage, but that from this point the coui'se of 

 development ceases to exhibit anything in common with that of the Crus- 

 tacea \ under these circumstances I have thought it better to call the clieli- 



* Journ. A. S. B., Vol. XL, Part II, p. 224. 

 t Jcuaiachc Zcitscliriit, 18G9. 



