178 Dr. T. Wright on Fossil Echinoderms 



below, the interambulacrum forms another prominence marked by 

 two concave depressions on each side thereof, from which a wide, 

 gently sloping central space occupies the middle of the ventral sur- 

 face, having the large transversely-oblong mouth-opening with its 

 projecting posterior lip occupying the anterior third of the base ; 

 on the sides of this sloping central space the basal portions of 

 the postero-lateral interambulacra are thickly studded wit 

 large slanting perforated tubercles, arranged with much regu- 

 larity in this region, and a few smaller tubercles are scattered 

 over the basal portion of the antero-lateral pair ; the crescentic 

 depressions below the anus have each a group of perforated 

 tubercles, and between them and the smooth central concave 

 portion of the base is the subanal fasciole, which forms a trans- 

 verse band in the middle, and a crescent on each side, the upper 

 cornua of which approaches the anal opening ; below the fasciole 

 there is another group of small perforated tubercles and a 

 copious granulation ; the crescentic depressions, subanal fasciole, 

 and this group form together a triangle, the base of which lies 

 before the anus, and its apex points towards the mouth ; around 

 this opening five pair of short poriferous zones indicate the 

 termination of the ambulacral areas. ^^ 



Affinities and differences. — The form of the ambulacral area^^ 

 the shortness of the anterior poriferous zone, and the size and 

 depth of the areolar spaces around the cylinders of the large 

 tubercles, together with the carinated elevation in the middle of 

 the interambulacrum, form a group of organic characters which 

 sufficiently distinguish this species from its congeners. In Spa- 

 tangus Desmarestii, which is found with S. Hoffmanni in the 

 same beds in Westphalia, the size of the test, the absence of very 

 deep areolas on the dorsal surface, the equal length of the pori- 

 ferous zones of the anterior ambulacra, and the much smaller 

 tubercles at the base, easily enable us to distinguish it from 

 S. Hoffmanni, ^ 



Stratigraphical range and localities. — It is found at Malta in 

 bed No. 4, the calcareous sandstone, and in Westphalia ; it has 

 been collected from the Miocene at Doberg near Biinde, and at 

 Astrapp near Osnabruck. 



Spatangus De Koninckii, Wright, n. sp. 



Test cordate, depressed before, elevated behind by the develop- 

 ment of dorsal and basal median carinse on the single inter- 

 ambulacrum ; ambulacral areas short and broadly petaloid; 

 anteal sulcus slight; depression of the single ambulacrum 

 inconsiderable ; several large tubercles between the petaloidal 

 ambulacra; posterior border obliquely truncated downwards 

 and forwards ; anal opening large and circular ; basal tubercles 



