( L^ PKASTER. , 21 



Doderlein of Strassburg for the loan of specimens representing his Japanese 

 species and for his kindness in answering questions and expressing opinions on 

 the vaHdity of certain forms. Through his kindness, I have been able to accept 

 his opinion that the genus Alexandria of Pfeffer is a synonym of Clypeaster, 

 being based apparently upon a specimen of the species here called humilis. 

 And we are further agreed that C. clypcus and C. excelsior of Doderlein are 

 synonyms of his C. japonicus. The clypeastroid described by Yoshiwara as 

 C. ogasaivaraensis is also C. japonicus. Dr. Seitaro Goto of the Imperial Uni- 

 versity, Tokyo, was so good as to have the type specimen sent to me and I am 

 thus able to reach a positive conclusion. For his courtesy, I take pleasure in 

 thanking Dr. Goto. 



Owing to Loven's attempt (1887, Bih. K. Svenska Vet.-Akad. Handl., 

 13, afd. 4, no. 5, p. 171-176) to apply Linne's names rosaceus and reticulatus 

 to species, with which they had never been associated, most unfortunate con- 

 fusion has crept into the nomenclature of the genus. For this reason it has 

 seemed to me important to give a certain amount of synonymy under the species 

 which have long been known, especially since Loven's combinations and deter- 

 minations have been incorporated into so widely used a text-book as Bronn's 

 Thier-reichs. 



Specific distinctions in the genus are based upon the form of the test, particu- 

 larly with reference to the thickness of the margin and the ratio of length to 

 breadth, upon the position of the anus, upon the form, relative length and open- 

 ness of the petals, and upon the tuberculation of test, particularly as shown 

 in the anterior ambulacrum, between the pore-pairs. These features are, of 

 course, more or less variable, especially the form of the test, yet even in the 

 most variable species there seem to be fairly well-defined limits. Few of the 

 species are hard to recognize and it is probable that the number of valid species 

 is larger rather than smaller than that listed here. 



Wliile the spines and pedicellariae are only of secondary importance in dis- 

 tinguishing the species of Clypeaster, so little has hitherto been published about 

 them, that a few notes may be inserted here. The primary spines are usually 

 smooth (PL 122, figs. 4, 9, 11) but in europacificus, rotundus (PI. 122, figs. 5, 6), 

 subdepressus, and prostratus, they are more or less rough or serrulate near the 

 tip; in some other species serrations are often found near the tip of the larger 

 primaries (PI. 122, figs. 14, 15). In lamprus (PI. 122, figs. 1-3), many oral pri- 

 mary spines are conspicuously elongated and broadly flattened at the tip, unhke 

 any spines found in other species. In some species, notably pallidus (PI. 122, fig. 



