144 SALENIDyE 



from those of the latter, and without these appendages it is impossible to distin- 

 guish the test of the one Urchin from that of the other, and the same conditions 

 may be true of the tests of other, nearly allied forms. C. WethereUi may be con- 

 sidered a variety of C. coroUare until proof to the contrary is discovered ; but the 

 structure of the test of C. spatuliferum and the remarkable form of its flattened spines, 

 when compared with the test and spines of C. coroUare, afford presumptive evidence that 

 they are distinct forms. It is very desirable to diminish the number and correct the 

 synonyms of species in our lists ; to do this, however, correctly requires much literary 

 research and a critical examination and comparison of the specimens themselves, before 

 a true solution of the difficulty can be arrived at ; and in doing all this the best ob- 

 servers very often confuse analogy with identity of structure, from the imperfect materials 

 upon which they are too often obliged to work. 



LocaJUy and Slratigrapldcal Position. — Cyphosoma striatum is usually found in the 

 hard, gritty beds of Lower Chalk near Folkestone, and occasionally in the Upper Chalk 

 with flints in Sussex. 



The type specimen figured in PI. XXIX belongs to the Museum of the Royal School 

 of INIines. I have examined several others collected by my kind friend, the Rev. T.Wiltshire, 

 F.G.S., from the Lower Chalk, near Folkestone, where he found it associated with 

 Salenia granulosa, Forb. 



SALENID.E. 



Family 5. — Salenid^, Wright, 1856. 



This natural family nearly corresj)onds to the Salenies of MM. Agassiz and Desor, and 

 is distinguished from other families of the Echinodea Endocydica by the peculiar structure 

 and great development of the apical disc, which, besides the five genital and five ocular 

 plates, has an additional or sur-anal plate, developed in the centre of the disc, immediately 

 before the anal opening ; this plate in some genera is single, in others it is composed of 

 from one to eight separate elements. 



The test is thin, and in general small, spheroidal, hemispherical, or depressed ; the 

 ambulacral areas are always narrow, straight, or flexuous, with two rows of granules or 

 small tubercles, that alternate with each other on the margins of the area. 



The poriferous zones are narrow ; the pores unigeminal, except near the peristome, where 

 they fall into oblique ranks of threes. 



The inter-ambulacral areas are wide, with two rows of primary tubercles, which have 

 large bosses and crenulated summits ; in Acrosalenia and Pseudosalenia the tubercles are 

 perforate, in Peltastes, Goniojjhorus, and Salenia they are imperforate. The mouth-opening 

 differs in size in the different genera ; the peristome is more or less decagonal, and 



