486 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



developed so as to give six arms to a ray arranged in 2,1,1,2 order. All the division 

 series are 2. The elements of the IIBr and IIIBr series of adjacent postradial series 

 are closely appressed laterally with sharp lateral edges and flattened sides. The 28 

 long and slender arms are 80 mm. in length and consist of about 150 brachials, of which 

 the lower are discoidal and the rest shortly triangular, gradually becoming oblong, but 

 always much broader than long. Syzygies occur between brachials 3+4, again from 

 between brachials 17+18 to between brachials 22+23, and distally at intervals of 

 from 9 to 17 muscular articulations. P! is about 7 mm. long and is composed of about 

 20 segments, which are but little longer than broad. P 2 is much stouter, reaching 14 

 mm. in length and consisting of nearly 25 rather longer segments. P b is similar but 

 rather smaller. P 3 is 6 mm. long with nearly 20 segments. P 4 is but little shorter 

 than P 3 but consists of only a dozen segments. The disk is 12 mm. in diameter, 

 naked, and rather incised. Sacculi are abundant along the pinnule ambulacra. The 

 color in alcohol is a mixture of brownish white and greenish gray. I examined this 

 specimen at the British Museum in 1910. It has 30 arms. None of the cirrus seg- 

 ments are quite so long as broad. 



Carpenter said that similis stands very close to brevicuneata, and it was with some 

 hesitation that he separated them. The large size of the centrodorsal and the lateral 

 flattening of the postradial series appear in both types. But in similis the greater 

 part of the IB^ is concealed, which is not the case in brevicuneata, while the lower 

 pinnules are smaller in brevicuneata, though it is individually of larger size and has 

 IIIBr series developed on all the IIBr series instead of on the outer side of each ray 

 only. In similis P 4 is similar to and of almost the same length as P 3 , whereas in 

 brevicuneata it is a good deal shorter and has a smaller number of segments. It is 

 in the relative proportions of these pinnules and the characters of the IBr! that the 

 chief difference between the two types presents itself. 



Three other specimens from Challenger station 174 were considered by Carpenter 

 as representing a new species that he called Antedon occulta and described in the fol- 

 lowing terms: The centrodorsal is a thick disk reaching 6 mm. in diameter and bearing 

 marginal cirri. The cirri are XXXV-XLV, 25-30. The segments are tolerably 

 uniform, and the later are compressed laterally with a slight dorsal keel which passes 

 into a faint opposing spine. The radials are entirely concealed, together with the 

 greater part of the IBri and also part of the IBr 2 (axillaries). The postradial series 

 may divide four times. The lower ossicles of adjacent postradial series are in close 

 lateral contact and somewhat flattened, but are not specially straight edged. All the 

 division series are 2, and the axillaries are often somewhat asymmetrical. The 36-48 

 arms are up to 110 mm. long and are composed of about 170 smooth segments, of which 

 the first few are oblong and those following are shortly triangular, gradually becoming 

 oblong again but remaining much broader than long until near the end of the arm. 

 Syzygies occur between brachials 3+4, again from between brachials 14 + 15 to be- 

 tween brachials 31+32, and distally at intervals of from 8 to 18 muscular articulations. 

 The lower pinnules of the inner arms are generally rather smaller than those on the 

 outer arms of each IIBr group, and more especially than those on the outermost arms 

 of each postradial series. PI may be 7 to 9 mm. long, with 20-25 segments, the lowest 

 of which are rather broad. P 2 reaches 10 or 15 mm. in length and may have 30 

 segments, the first half of which are very stout. P 3 is sometimes nearly equal to P 2 , 





