92 Dr. T. Wright on Fossil Echinoderms 



single row of pores, flanked by a row of tubercles on each side, 

 with a space between tilled by a microscopic granulation; it is 

 abruptly bounded below by the fasciole, and terminates at the 

 disc in a blunt lancet-shaped apex. The antero-lateral ambulacra 

 in the large specimen are f^ths of an inch longer than the pos- 

 terior pair, and form an angle of 37 with the transverse line 

 through the disc ; they are round at the base and blunted at the 

 apex, and the anterior side is more rounded off than the pos- 

 terior for the reception of the apex of the ambulacrum ; in the 

 anterior zone there are twenty, and in the posterior zone twenty- 

 four pairs of holes. The postero-lateral pair describe an angle of 

 55; both pairs form concave valleys; the pores in the zones are 

 of the same size, and are pierced so wide apart (1 c) that the pores 

 of each pair are nearly as distant from each other as the width of 

 the space which separates the two avenues ; in the anterior am- 

 bulacral avenues there are twenty in the anterior and twenty-four 

 in the posterior zone; in the posterior pair the numbers are 

 twenty-two before and eighteen behind. The peripetal fasciole (1 e) 

 has an unequal width in different parts of its track ; it is narrow 

 where it passes over elevations of the test, or is bent into angles, 

 and becomes wider in other parts of its course. The apical disc 

 (1 ) is small, heart-shaped and central ; the two anterior genital 

 holes are smaller and placed closer together than the posterior 

 pair ; the five eye-holes as usual are situated at the summit of 

 the ambulacral apices : the madreporiform tubercle occupies the 

 surface of the posterior triangular genital plate. The anus is a 

 large oblong opening, situated in the upper half of the posterior 

 border, at the distance of /^ths of an inch from the fasciole in 

 the small individual. The base in both specimens is concealed ; 

 the tubercles (Id) are small, crenulated and perforated, and nearly 

 of the same size ; a few larger ones occupy the sides of the an- 

 terior ambulacral sulcus ; the sides of the ambulacral areas and 

 as much of their basal portions as is exposed are destitute of 

 tubercles. 



Affinities and differences. Brissopsis Ducici is readily distin- 

 guished from the other forms of this genus met with in the 

 Maltese beds, by the full development of its ambulacral areas, 

 their straightness, width and depth. The double crescent formed 

 by the ambulacral areas in B. crescenticus is a sufficient character 

 by which it may at a glance be distinguished from B. Duciei. 



Locality and stratigraphical position. This species was col- 

 lected from bed No. 1, the Gozo marble, at Malta, where it is rare ; 

 the two specimens before us are the only ones we have seen. 

 We dedicate this fine species to the Earl Ducie, whose valuable 

 collection of Maltese fossils has added to our previous knowledge 

 of the palaeontology of the island, and whose geological map of 



