86 Dr. T. Wright on Fossil Echinoderms 



superficial layer of the calcareous plates, which carries all the 

 fine sculpture of the test, is almost entirely denuded from the 

 dorsal surface ; one or two fragments alone remain to show that 

 the tuberculation was minute and close-set. 



Affinities and differences. This species is distinguished from 

 S. Hoffmanni by the excessive elevation of the posterior part of 

 the test ; by the shorter, wider and more oval form of the peta- 

 loid ambulacra ; by the poriferous zones of the anterior pair 

 being more complete ; by the large dorsal tubercles being smaller 

 and fewer in number ; by having a less impressed anteal sulcus ; 

 a convex base, with smaller tubercles ; a ridge-like projection, 

 with a regular tuberculation of the basal portion of the inter- 

 ambulacrum, with smooth naked ambulacral tracks on each side 

 thereof. From S. Desmarestii it is distinguished by its short, 

 broad, petaloidal ambulacra, which are long and attenuated in 

 S. Desmarestii ; by the greater size, number and regularity of 

 the large dorsal tubercles, which are few, small and scattered in 

 S. Desmarestii', the posterior region is not at all elevated in S. 

 Desmarestii, and the anus is transversely oblong, whilst in S. 

 De Koninckii the posterior part is much elevated, and the anal 

 opening is round. 



S. Desmarestii has a few groups of large tubercles on the 

 upper part of the single interambulacrum, which are entirely 

 absent both in S. Hoffmanni and S. De Koninckii. The basal 

 region is so much covered up with matrix in the specimen of S. 

 Desmarestii before us, that we cannot institute a comparison 

 between this portion of its test and that of S. De Koninckii. 



Locality and stratigraphical range. The two or three speci- 

 mens we have seen in the Earl Ducie's cabinet were collected 

 from the clay bed No. 2 at Malta ; they have all a deep ferru- 

 ginous colour, and are not well preserved. We dedicate this 

 species to our friend Dr. De Koninck of Liege, the learned 

 author of several memoirs on the paleontology of the carbo- 

 niferous rocks of Belgium. 



Genus BRISSUS (Klein, 1734). 



Form oval; the ambulacral summit excentral, and situated 

 near the anterior border ; the antero- and postero-lateral ambu- 

 lacral areas straight, and lodged in shallow depressions of the 

 test ; the anterior pair are nearly transverse, the posterior pair 

 deviating slightly from the longitudinal direction. The single 

 ambulacrum very simple in structure ; no anteal sulcus ; the 

 peripetal fasciole very sinuous ; mouth large, labiate, and near 

 the anterior border ; anal opening large, situated in the middle 

 of the posterior surface ; the subanal fasciole approximated close 



