158 A. E. Verrill — Revision Genera and Sj^ecies of Starfishes. 



The following species apparently belong to the genus as restricted 

 by Gray (1840): 



jP. pulchellus Gray. New Zealand to China. 

 P. ahnormale Gray. Unknown locality. 

 P. Bourgeti Perrier. Cape Verde Islands. 

 P. Gunnii Perrier. Tasmania and Australia. 

 P. Duheni Gray. South and West Australia. 



Tosia Gray, 1840. Type T. ausU-alis Gray. 



Astrogonium (pars) Miill. and Troscliel, Syst. , Ast. , ] 842. 

 Tosia Gray, Synopsis, p. 11, plates iii and xvi, 1866. 

 Pentagonaster (Sec. A, b, pars) Perrier, Revision, p. 30, 1876. 

 Pentagonaster (pars) Sladen, Voy. Chall., xxx, p. 264, 1889. Perrier, Exp. 

 Trav. et Talism., pp. 389, 390, 1894. 



Under the ordinary rules of priority, in zoological nomenclature, 

 there is no valid reason why Tosia should not be adopted for a large 

 part of the species included by Perrier and by Sladen in the genus 

 Pentagonaster, providing we are to consider this group generically 

 distinct from Pentagonaster Gray. This question of the generic dis- 

 tinction must still be regarded as doubtful by many students of the 

 group, though Perrier, in his later works, has definitely separated 

 them, as shown above. 



The only obvious difference, hitherto pointed out, that may be 

 considered as of generic value, is the gradual decrease in size of the 

 marginal plates distally, so that the rays are sub-acute, instead of 

 the distal ones being larger and swollen, as in the true Pentagonaster. 



But there are species of, the latter in which the distal plates are 

 only slightly larger than the others, while the amount of decrease 

 in the plates of the species of this group is variable. Moreover in 

 the restricted genus Goniaster, one species [G. Afvicanus, type) 

 has the distal dorsal plates more swollen and larger than those that 

 precede it. 



Nevertheless, since the marked enlargement of the distal plates 

 indicates a different law of growth in species so characterized, it 

 seems desirable to keep the two groups separate, at least until truly 

 intermediate forms become known. 



In the typical species of Tosia, the marginal, abactinal, and 

 usually some of the actinal plates have a naked central area, with 

 one or more rows of granules around the margin. But the extent of 

 the granulation varies more or less individually, and also according 

 to the age of the specimen. Therefore we cannot regai'd this as a 

 matter of much importance, generically. 



