180 Notices of Memoirs — By Dr, C. Lutken. 



accuracy, and profound knowledge which is peculiar to the works of 

 the celebrated Scandinavian zoologist. 



The genus Leslcia is described, in 1851, by Dr. J. E. Gray, in the 

 ''Annals," and subsequently, in 1855, in the "Catalogue of Recent 

 Echinida," from specimens from Lugard, in Mr. Cummings' collec- 

 tion. It is most intimately allied to the Spatangidce, of which it has the 

 general stamp, but is distinguished from them, and therefore the type 

 of a peculiar family (Lesldadce Gray) or tribe {Falceostomata Loven) 

 by the peristome and periproct being closed up with a few "trian- 

 gular converging valves," those of the vent with some small "spicula" 

 in the centre. Dr. Gray has already remarked that " in the form of the 

 mouth and vent it has considerable affinity with the fossil Cystidea, 

 especially the genus Echinosphcerites.'^ The detailed description given 

 by Prof. Loven quite confirms this remarkable combination of fea- 

 tures ; the characters assigned to the " Palceostomata'' are as follows : 

 testa oviformis, peristomium non lahiatum, pentagonum, (squilaterale, ore 

 qmnqueralis, anus intra periprostium centralis, valvis clansur quinque- 

 octo ; apertvrce genitales hince ; semita unica peripetala.'^ Leskia is a 

 true Spatangoid, save the mouth and the vent; the latter, instead of 

 being surrounded by a threefold circle of minute plates, the greater 

 and outermost, has only 5, 7, or 8 great triangular outer plates, and 

 an equal number of minute inner papillee. The peristome is not 

 bilabiate with a prominent under -lip, nor is it formed principally by 

 the ambulacral plates ; it is pentagonal, and bordered almost exclu- 

 sively by the interambulacralia ; there is no buccal membrane covered 

 with three to five series of irregular plates, decreasing inwards, but 

 the mouth is closed up by five equal triangular plates, inserted on 

 the five sides of the peristome. "No living Echinid has such a 

 mouth ;" but the author thinks that the genus Toxaster of the " Neo- 

 cromien Inferieur," whose peristome was pentangular, not labiate 

 might possibly — though the configuration of its mouth somewhat 

 more approaches to that of the true Spatangidm — have had a similar 

 organization. 



In the Silurian Cystidea again, we find precisely the same structure 

 as in the recent East Indian Sea-urchin, viz., in the commonly so- 

 termed "ovarian pyramid," which, after the opinions of Gyllenhal, 

 Wallenberg, Pander, Hisinger, de Koninck, and Billings, is really the 

 mouth, whilst von Buch, with some inconsequence, makes it the mouth 

 of Caryocrinus, but the genital outlet in the other Cystidea, and Joh. 

 Miiller and Volborth sought the mouth in the centre of the converg- 

 ing ambulacral furrows. The remarkable observations on Sphceronites 

 pomum and Echinoy cheer ites aurantium, by means of which Prof. 

 Loven draws the conclusion that Leshia is a Spatangoid with the 

 mouth of a Cystidean, we will give with his own words. 



"Good specimens of Sphceronites pomum GylL, collected by Prof. 

 Angelin, show its organization more distinctly than usual. He had 

 observed that this animal had no stalk, but adhered immediately to 

 rocks or other objects through a part of its lower surface, which is 

 without pores, and surrounded by a ridge formed of the somewhat 

 thickened, free, smooth border of the undermost plates. This sur- 



