from the Island of Malta. 1 85 



assumes : the mouth is large, near the anterior third of the base : 

 the anus is of an elliptical form, and occupies more than the 

 upper half of the truncated portion of the posterior border. The 

 peripetal fasciole (2 a) closely embraces the ambulacral pairs, and 

 makes three angles in passing over the anterior interambulacra ; 

 the subanal fasciole (2 h) describes a heart-shaped outline, its base 

 is near the anus, and its apex touches the prominent point of the 

 sternum ; the space thereby circumscribed is tilled with tubercles 

 having a definite arrangement. Tiic apical disc is small, with 

 four genital pores, the posterior ])air being much larger than the 

 anterior pair; the tubercles (2c) on the anterior interambulacra are 

 much the largest, those on the rest of the back are small and 

 very uniform in size, whilst those on the sternum and the sides 

 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 Brissopsis (Agassiz, 1840). 



Form elongated, subcyliudrical ; 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.). PI. VI. fig, 1 a-e. 



Test oblong, depressed anteriorly, elevated posteriorly ; apical 

 disc 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 

 3y'*o inches, transverse diameter 3y% inches : height cannot be 

 accurately measured. 



