REPORT ON THE CRINOIDEA. 251 



A syzygy in the second brachial, and the next between the sixth and fourteenth ; 

 others at intervals of three to twelve joints, the intervals often becoming shorter towards 

 the end of the arm. 



The second distichal and the first palmar (or brachial) bear tolerably equal pinnules 

 of about fifteen stout joints, the five lowest of which are rather broad and trihedral, with 

 flattened outer faces and the inner sides slightly bevelled away. The second and third 

 brachials have smaller pinnules with fewer joints, the basal ones being more compressed ; 

 and the following pinnules are larger again, with broader lower joints, the outer edges of 

 which are expanded towards the ventral side. This arrangement gradually dies away 

 in the outer parts of the arms, and the joints become more elongated. 



Disk slightly incised and well plated, like the brachial ambulacra ; the pinnule- 

 ambulacra have well-defined side plates and small sacculi. 



Colour in spirit, — dark grey-brown. 



Disk 15 mm.; spread probably 30 cm. 



Locality. — Station 344, April 3, 1876; near Ascension; lat. 7° 54' 20" S., long. 

 14° 28' 20" W.; 420 fathoms ; volcanic sand. Four broken specimens. 



Remarks. — This species cannot well be mistaken for any other, as it is the only 

 tridistichate Antedon with a syzygy in the second brachial (PI. LII. fig. 3); though the 

 type is common enough in the genus Actinometra (PI. LX.; PI. LXII. fig. 3). The 

 four specimens obtained were all much mutilated, the arms having broken away at 

 the syzygy in the second joint above the distichal axillary. In some cases this was the 

 hypozygal of the palmar axillary, but as only a few arms are preserved it is impossible 

 to determine their number, or whether palmar axillaries occurred in all the specimens. 

 Under these circumstances therefore I have thought it best to enclose the palmar sign 

 within brackets in the specific formula. 



The length of the cirri and the strong dorsal processes on their numerous joints are 

 also good distinctive characters of the type. One cirrus, as shown in the figure (PI. LII. 

 fig. 3), has been fractured and subsequently regenerated, a somewhat rare occurrence, as 

 I have already remarked on p. 203. The characters of the pinnules of Antedon porrecta 

 are the same as those of Antedon basicurva and its allies, though in a less marked 

 degree. The lower joints of the genital pinnules are expanded towards the ventral side 

 so as to protect the genital glands, which have but a slight covering of anamljulacral plates, 

 while the first two pinnules have massive lower joints with the outer sides flattened just 

 as in Antedon valida and Antedon incerta (PI. XV. figs. 5, 6 ; PI. XVIII. fig. 5). 



Apart from its general specific characters Antedon porrecta is remarkable as being 

 one of the few Atlantic species of the genus which have an amljulacral skeleton. It 

 was obtained in the neighbourhood of Ascension, together with the dimorphic Antedon 

 multispina, which also occurs near Tristan da Cunha, and they thus serve as a con- 



