434 ME. W. p. SLADEN" ON THE ASTEEOIDEA 



fixet, the tout ensemlle of the spinulation, dispose me, after careful 

 study of this limited material, to regard the starfish as present- 

 ing a well-marked locational variety of the A. ruhens type. And 

 although these structural modifications are not such as would 

 command more special recognition, the divergence seems one 

 which is well worthy of record in a morphological point of view. 



ECHINOIDEA. 



Steongtlocewteottjs i]srTEEMEDius {Barnes), A. Agassiz, 



1863. Psammechinus intermedius, Barnes, in A. Agassiz, Proc. Acad. 

 N. S. Philadel p. 357. 



1866. Boletia radiata, von Martens, Ostasiat. Echin., Wiegm. Archiv, 

 Jahraj. 32, p. 136. 



1872. Strongylocentrotus intermedius, A. Agassiz, Rev. Echini, III. 

 Cat. M. C. Z. p. 164. 



Toxopneustes grandiporus, Lutlcen {MS. Copenhagen Mus.), fide A. 

 Agassiz. 



Coll. St. John : lat. 34° 8' N., long. 126° 24' E., Korean Straits, 

 24 fathoms. 



Owing to its dense clothing of short moderately uniform spines, 

 this Echinoid bears a great resemblance in facies to SpJicerecMnus. 

 The resemblance, however, is merely superficial, as neither the 

 tubercles nor the spines are equal-sized, nor are the former closely 

 packed upon the plates or arranged in strictly horizontal rows ; 

 the gill-slits are very slight, being little, if at all, more deeply in- 

 dented than generally in Strongylocentrotus. In none of the above- 

 mentioned details, which are regarded as stable generic characters 

 in SplKErecJiinus, does the present sea-urchin agree ; and although 

 it resembles that genus in possessing only four pairs of pores to 

 each arc, their mode of arrangement does not differ essentially 

 from that of Strongylocentrotus. 



The poriferous zones are nearly as broad as the median am- 

 bulacral area, which at the ambitus bears four vertical ranges 

 of tubercles — the outer ones, which stand next to the poriferous 

 zones, being much larger than the inner series. On the interam- 

 bulacral plates there are three primary tubercles, the middle one 

 longest ; and this alone remains prominent up to the apical disk, 

 whilst the companion tubercles diminish very rapidly on the ab- 

 actinal surface, being wanting altogether or represented only by 

 small miliaries on the uppermost plates. There are also two or 

 three large secondaries and a moderate sprinkling of miliaries 



