200 VERRILL 



depend very closely on the size. One of the largest of this lot has 

 the radii 70 mm. and 275 mm. Some young specimens, not more 

 than 30 mm. in diameter, already have sixteen rays; while others, 

 200 mm. in diameter, have no more. 



It is said, on good authority, to become over four feet in diameter. 

 In that case, it is probably the largest starfish known. The largest 

 that I have seen are over two feet in diameter. Large specimens 

 are hard to preserve, and for that reason are seldom collected. 



TERATOLOGY. 



The budding in of new rays does not always proceed in a regular 

 bilateral manner by pairs. I have studied several young specimens 

 in which, in addition to the regular pairs, one or two new rays had 

 appeared irregularly in different places. If one odd ray appears it 

 gives rise to an odd total number of rays; for if the young start 

 with six rays and a pair of new rays appears each time, the final 

 number must be even. One specimen before me, eight inches in 

 diameter, has nineteen equal and regular rays, with a pair of small 

 budding rays placed regularly. Such an individual may have had 

 seven rays at first instead of six. In most cases the first pair of 

 interpolated rays appears either side of a single ray, with five rays 

 on the other side. This indicates that the original number of rays 

 in the young is normally six. But in the case just cited there are five 

 posterior rays, as usual, while there are fourteen (seven pairs) in 

 front, indicating that at first there may have been two front rays, or 

 seven altogether. This may be the manner of origin of some speci- 

 mens with odd numbers of rays. But I have seen no very young 

 ones of this sort. Should one bud be suppressed, or two buds 

 appear together on one side, in place of one, the final result would 

 be the same. 



I have studied very young ones in which one bud is suppressed 

 (see pi. LXXV, fig. i). One young example (pi. LXXV, figs. 3, 3a) 

 has the madreporite much larger than usual. It has an oblong disk 

 and eighteen somewhat unequal rays. It looks as if about to divide 

 autotomously. Its disk is 15 mm. by 12 mm. in diameter. The 

 arrangement of the rays and new buds in this specimen is peculiar 

 and anomalous. Three very small rays, nearly identical in size and 

 structure, are developing simultaneously at three places. Two of 

 these are in the normal position, and separated by seven nearly 

 equal rays. Then follow, on one side, two larger rays succeeded by 

 a small, extra, budding ray ; on the other side no such bud appears. 



