from the Island of Malta. 91 
of the base are intermediate in size; the basal tracts of the am- 
_bulacral areas are destitute of tubercles; as they approach the 
mouth they are again perforated with a single row of holes; 
those of the antero-laterals extend as far as the border, whilst 
the single and posterior pair have only two or three pairs of their 
plates perforated. 
Genus Brissoprsis (Agassiz, 1840). 
Form elongated, subcylindrical ; ambulacral areas straight, 
short, and wide, converging near the summit of the test ; peri- 
petal fasciole flexuous, closely surrounding the ambulacral areas ; 
two or four genital pores, the posterior larger than the anterior 
pair ; five ocular plates disposed nearly equally apart in a penta- 
gonal form around the genital openings; subanal fasciole wide, and 
situate at a considerable distance below the anal opening ; single 
ambulacrum lodged in an anteal sulcus ; the basal portions of the 
ambulacra are wide and naked ; the tubercles are very uniform 
in size, and are crenulated and perforated. Three living species ; 
the rest are fossil in the tertiary rocks. 
Brissopsis Duciei (Wright, n. sp.). Pl. VI. fig. 1 a-e. 
Test oblong, depressed anteriorly, elevated posteriorly ; apical 
dise central; ambulacral areas forming concave depressions ; 
single ambulacrum the longest and widest ; antero-lateral pair 
straight, angle of inclination 34°; postero-lateral shorter, angle 
of inclination 55°; peripetal fasciole broad and undulating ; 
anus oval, large, situated high on the border ; base concealed ; 
dorsal tubercles small, nearly of a uniform size, except on the 
sides and the anterior part, where they are larger. 
Dimensions. — Large specimen. Antero-posterior diameter 
3,5 inches, transverse diameter 3,4 inches: height cannot be 
- accurately measured. 
Small specimen. Antero-posterior diameter 1,9, inch, trans- 
verse diameter 137 inch; height over the middle of the single 
ambulacrum ;%ths of an inch, at the highest point of the dorsal 
region 1,4, inch. 
Description.—This beautiful Urchin is one of the most typical 
. forms of the group to which it naturally belongs. The test is 
oblong and inclined, from the height of the anterior third being 
less by ;4;ths of an inch than the posterior third; the ambu- 
lacral areas are all well developed, and arranged in the form of a 
St. Andrew’s cross ; as the apical disc is situated near the centre 
of the body, the regularity of their arrangement forms a con- 
spicuous character of this species. The anterior ambulacrum (1 a) 
is concave, and makes an inconsiderable anteal sulcus ; there is a 
