ii ' INTRODUCTION. 



Among the family Urasterid^e a small specimen belonging to the genus Ur aster 

 has been found in the Porest Marble of Wilts, of which I have given figures. 



The Ophiuroidea have been quite as scarce as the true Star-fishes. The " Avicula 

 contorta beds" Upper Trias, at Hildesheim, were found to contain specimens of 

 Opldolepis Damesii, Wr., a species which I first described from specimens sent for 

 my determination from the Berlin Museum by Dr. Dames. These notes were subse- 

 quently translated and inserted in ' Der Zeitschrift der Deutschen geologischen Gesell- 

 schaft,' Jahrgang, 1874, with an excellent figure of the species. A few months later the 

 same Brittle-Star was collected from the black shales belonging to the Bone-bed series at 

 Westbury-on-Severn, and soon afterwards similar black shales above the Bone-bed near 

 Leicester yielded remains of the same species. 



After my additional plate had been printed, and the last sheet of this volume been 

 twice revised, I received, on the 3rd inst., from my friend Professor Buckman, F.G.S., 

 of Bradford Abbas, for description in the ' Proceedings of the Dorset Naturalist Pield 

 Club/ a specimen which he had collected from the Calciferous Grit at Sandsfoot Castle, 

 near Weymouth. This appears to me to be a new Ophiurella from our Corallian strata, 

 and I have had it drawn on wood and inserted in its natural place in the text. 



I have grouped the Asteroidea into four families — I. Urasterid^e; II. Tropi- 

 DASTERiUiE ; III. GoNiASTERiD^ ; and IV. AsTROPECTiNiD^. Of these, Urasterid^e 

 and Tropidasterid^ (not defined in the text) may receive the following diagnosis : — 



The URASTERiDiE, Wright, have a stellate, five-rayed body ; the rays are round or 

 angular and abundantly covered with spines. The ambulacral areas are lanceolate and 

 bordered by several rows of spines, and the upper surface of the disk and rays provided 

 with short, blunt, and thorn-like spines ; in some species they are sparsely distributed in 

 single rows, or in others closely set together in a linear arrangement on the disk rays. 

 The interspinous teguraentary is naked and perforated with pores for respiration ; there 

 are four rows of pores for the passage of the tubular feet, so that the pores have a 

 quadriserial arrangement in the avenues. The pedicellaria are supported upon soft 

 stems, and the opening of the vent is dorsal and excentral. This family ranges from the 

 Lias seas down into those of our own time, with so little variation in anatomical 



