REPORT ON THE CRUSTACEA MACRURA. 87 



The basccphysis is short, the extremity of the flagellum reaching to half the length of 

 the meros. The mastigobranchia is broad, bifid, and supports a slender full-plumed podo- 

 branchia. 



The branchiae generally consist of large and well-developed plumes, arranged as in 

 the annexed table : — 



Pleurobranchiae, 

 Arthrobranchiae, 

 Podobranchia?, 

 Mastigobranehia?, 



The mastigobranchiae have a pecubar notch or bend in the outer or posterior 

 margin ; in that of the second gnathopoda it is increased to a deep cleft. This curve or 

 excavation may be only a specific feature, but inasmuch as it does not exist in Palinurus 

 vubjaris, it may be of generic value, a point that can only be determined when other 

 species are examined. 



Habitat.— Station 135c, October 17, 1873; lat. 37° 25' 30" S., long. 12° 28' 30" W.; 

 off Nightingale Island, Tristan da Cunha ; depth, 100 to 150 fathoms; bottom, hard 

 ground, shells, gravel. One specimen. 



Length 248 mm. (10 in.). 



This species has been described under the name of Palinurus lalandii by Professor 

 Milne-Edwards, from a specimen of Lamarck's preserved in the museum, but, as far as I 

 am aware, it has never been figured. 



Two small specimens of what I believe to be the young of this species were taken 

 from the screw of the Challenger the day after she left the Cape of Good Hope. The 

 armature and ornamentation correspond with those of the adult. The specimen is 

 about 25 mm. in length, and appears to be perfectly formed in all except its sexual 

 characters. No foramen or opening could be detected on the coxa of either the third 

 or fifth pair of pereiopoda, whereas in the adult it is very conspicuous, more 

 especially in the male, where it is elevated on a prominent tubercle implanted close to 

 the pleural articulation. 



This small animal is one of considerable interest, inasmuch as it shows that Palinurus 

 arrives at its complete external form when it has only grown to an inch in length, having 

 by that time undergone all its morphological changes. The brephalos having quitted the 

 ovum in a Megalopa stage, in the form known as Phyllosoma, about 1*5 mm. or 2 mm., 

 in length, assumes the outward shape of its parent by the time it has reached the 

 length of one inch. 



Yet, while I write, I have before me a Phyllosoma nearly an inch long, in which all 

 the characters of the brephalos as it quits the ovum of Palinurus are present, excepting 

 the addition of new limbs. The question must therefore arise, whether our knowledge of 



