18 



NATURAL HISTORY BULLETIN 



ary spines are still quite bright bro^vnisli-red but in all the 

 other specimens this color is nearly or quite faded out and 

 they are yellowish or white. 



Mortensen (1910, Bull. 74 U. S. Nat. Mus., p. 13) has sug- 

 gested a distinct variety of ahyssicola, which he calls teretispina, 

 and of which he says (p. 15) "I am inclined to think it will 

 ultimately prove to be a distinct species." In deference to this 

 opinion, of my honored friend and colleague, I have carefully 

 examined more than 150 specimens of ahyssicola from ten dif- 

 ferent localities to see if I could distinguish this variety con- 

 sistently. While many specimens answer perfectly to the de- 

 scription and figures of teretispinu, and others are with equal 

 certainty typical ahyssicola, I cannot find any combination of 

 characters by which they can be separated consistently from 

 each other. Even the shape of the primary spines is unreliable 

 and indeed shows great diversity. Relatively few specimens 

 have the radioles "somewhat fusiform and attain their greatest 

 diameter at about one-fifth the length of the spine from the 

 base," and it is very unusual to have more than a few spines 

 on one specimen show this character clearly. Many specimens 

 have most of their spines cylindrical with a more or less in- 

 distinct constriction at the base, or very slightly fusiform with 

 the largest diameter at or near the middle. Sometimes the 

 greatest diameter of the spine is near the tip, but this is quite 

 unusual. In one specimen a primary spine on one interam- 

 bulacrum is notably stout and slightly thicker distally than 

 proximally, while the others are slender and nearly cylindrical. 

 Perfectly terete mature spines are very uncommon but imma- 

 ture spines are usually terete. Cylindrical spines, terete dis- 

 tally, such as characterize Mortensen 's proposed variety (see 

 his plates 9 and 10) are very "common and are often found on 

 specimens Avhich have most of the spines more perfectly cylin- 

 drical. So far as the tuberculation of the ambulacra and the 

 shape of the test is concerned, they are simply matters of 

 slight individual diversity, and instead of considering tereti- 

 spina as a potential species, I cannot even accept at as a variety 

 worthy of recognition. 



In the "Narrative" (p. 173) Dorocidaris hlakei A. Ag. is re- 



