LITHOTRYA RHODIOPUS. 363 



length of the whole cirrus. In a specimen in which the 

 sixth cirrus contained twenty- two segments, the caudal 

 appendages actually contained twenty. The segments 

 are thin, with their upper edges clothed with serrated 

 spines. The slip of membrane on each side, whence this 

 organ springs is united, for a little space, to the lower 

 segment of the pedicel of the sixth cirrus. 



Size and Colour. — Width of the capitulum rather above 

 ^ths of an inch ; length, including the peduncle, (con- 

 tracted by spirits,) nearly one inch. Valves, as usual, 

 dirty white, partly invested by yellow membrane, fur- 

 nished with a few minute yellow horny spines. Pedicels 

 of the first four cirri, caudal appendages, penis, the two 

 posterior thoracic segments, the segments of the cirri, and 

 the trophi, clouded, banded, or spotted, with blackish 

 purple. 



Affinities. — This species, in the characters derived from 

 the valves, comes perhaps nearest to L. Bhodiopus ; in the 

 characters derived from the animal's body, it is nearest to 

 L. dorsalis. 



4. LlTHOTRYA RHODIOPUS. PI. VIII, fig. 4. 



Brisx^us rhodiopus. J. E. Gray. Annals of Philosophy vol. x, 



(new series,) 1825. 



— — J. E. Gray. Spicilegia Zoolog., Tab. xvi, 



fig. 17, 1830. 



L. scutis terga ample obtegentibus : carince crista in" 

 ternd tenui, in parte superior e positd : lateribus, superjicie 

 interna symmetrice et late ovatd, carince latitudinis plus 

 quam tertiam partem cequantibus: tergorum basali apice 

 tenui, et angulo carinali producto : rostro et pedunculo 

 ignotis. 



Scuta largely overlapping the terga. Carina with a 

 slight central internal ridge in the upper part. Latera 

 with their internal surfaces symmetrically and broadly 

 oval, more than one third of the width of the carina. 



