Post-larval Development of the Spiny Lobsters. 443 



The remaining three species referred to Puerulus {P. p^tllu' 

 cidus, P. spiniger, and P. atlanticus) are all described from 

 specimens of small size (not exceeding 22 mm. length), and 

 this circumstance, together with the slight development of 

 the spines on the carapace and the general thinness of the 

 integument, suggests that they are immature forms. Ortmana 

 has discussed this possibility in describing P. spiniger {loc. 

 cit.), which Avas found together with small specimens of 

 PanuUrus versicolor (or, as Ortraann called it, P. polyphagus), 

 and which resembles that species in having no exopodite on 

 the third xnaxilliped. Oitmann notes, however, that the 

 young specimens of PanuUrus did not exceed in size those of 

 Puerulus, although the former had assumed the specific 

 characters of the adult in the spinulation of the carapace and 

 in other respects ; he infers that Puerulus spiniger cannot be 

 the young form of PanuUrus versicolor, and he further con- 

 cludes that the differences between the two genera are so 

 great that Puerulus, if not an adult, must be the young of 

 some hitherto undiscovered form of Palinurid. 



It appears to have escaped notice that these small species 

 of Puerulus agree exactly with Boas's * description of what 

 he calls the " Natant "-stage of the Palinuridas. Boas found 

 vestiges of exopodites persisting on the thoracic legs of some 

 of his specimens, and he further notes that they retained 

 larval characters in the relative shortness of the antennular 

 peduncle, in having the third maxillipeds separated from each 

 other at the base, and the maxillipeds and maxillse soft, 

 sparsely setose, and of embryonic appearance. The absence 

 of the " cervical " groove (c), the presence of lateral ridges, 

 and the small number of spines on the carapace are also 

 mentioned, and an important larval character was found in the 

 persistence of coupling-hooks on the appendix interna of tiie 

 pleopods. The specimens measured up to 25 mm. in length. 

 Boas also mentions that he had examined specimens of 

 young Palinuridae of about the same size as those in the 

 Natant-stage, but agreeing with the adult except in the 

 absence of sexual characters. 



authors) as lacking the first pair of pleopods. I overlooked the fact that 

 these appendages are described as present in the female of PuHnurellus 

 by Boas (Kgl. Dauske Yidensk. Helsk. Slir. (6) i. pp. 92 & 183 (188U), 

 and Zool. Anz. v. p. 113, 1882) and by Spence Bate (Ann. & Mag. Nat. 

 Hist. (5) vii. p. 220, 1881). I find that they are also present in a male 

 specimen belonging to this genus in the British 3Iuseum collection. 



« "Studier over Decapodernes Slaegtskabslbrhold," Kgl. Danske 

 Yidensk. Selsk. Skr. (6) i. p. S3 (1880j. 



