190 Dr. T. Wright on Fossil Echinoderms 



the antero-lateral ambulacra, which are likewise slightly curved 

 forwards, in the length and depth of the posterior pair, which 

 equal the single ambulacrum in length, in the breadth and extent 

 of the peripetal fasciole, and the perpendicular truncature of the 

 posterior border, with the general tumidity of its sides, that it is 

 readily distinguished from them. 



Locality and stratigraphical position. — It was collected from 

 bed No. 4, the calcareous sandstone at Malta, and is one of the 

 few tertiary Urchins in our cabinet ; it is the only specimen of 

 the species we have seen. 



Hemiaster Cotteauii, "Wright. PI. VII. fig. 2 a-d. 



Test orbicular, globose, much inflated, declining anteriorly, ele- 

 vated posteriorly, the interambulacrum forming a prominent 

 carina which terminates in a tail-like process above the anus ; 

 posterior border obliquely truncated ; ambulacral areas deeply 

 sunk ; an anteal ambulacrum forms the sulcus in the anterior 

 border; antero-laterals long, and inclined to 45°; postero- 

 laterals one-half the length of the anterior pair, inclined to 

 57°; apical disc nearly central; peripetal fasciole broad and 

 undulating ; anus high under the carinal process ; tubercles 

 larger on the sides and base than on the dorsal surface; 

 mouth labiate near the anterior border. 



Dimensions. — Antero-posterior diameter li^ inch, transverse 

 diameter 1^^ inch, height 1— inch. 



Description. — This Urchin has a globose form, and is much 

 inflated at the sides; the dorsal surface is convex, and declines 

 much more rapidly from the apical disc to the anterior border, 

 than from the disc to the posterior border. The ambulacral 

 areas (2 a) are all deeply sunk ; the single ambulacrum is the 

 longest, and forms a considerable anteal sulcus; the antero-lateral 

 pair have a gentle double curve ; they are y^ths of an inch in 

 length, and form an angle of 45°. The number of poi*es (2 c) 

 in the avenues is twenty-two pairs in the inner, and twenty-four 

 in the outer zone ; the postero-lateral pair are scarcely half the 

 length of the anterior pair; they incline at 57°; their number of 

 pores is ten and twelve pairs. The peripetal fasciole (2 d) closely 

 embraces the ambulacral star ; a naked track proceeds from the 

 base of the antero-laterals to the mouth, indicating the course 

 of the imperforate portion of the ambulacral areas : the rapid 

 declivity of the anterior part of the test strongly contrasts with 

 the inflated condition of the sides and the elevation of the in- 

 terambulacrum ; from the centre of this area a ridge rises which 

 is produced into a tail-like process, and beneath, the posterior 

 border is scooped out, and truncated obliquely downwards and 



