86 CHARLES CHILTON 



but has the same general shape and structure. Evidently the very young male 

 in this species passes through a stage in which the second gnathopod is similar 

 to that of the female, in the same way as it does in Talorchestia deschayesii, 

 T. inartensii, etc. 



In all the specimens examined the pleopoda are well developed, double 

 branched, each branch consisting of numerous joints, I have not noticed any 

 difference between the shore forms and those taken at higher levels as regards 

 the size and development of the pleopoda. 



One of the males in tube No. 259 has both the lower antennae much 

 longer than usual and with an abnormal number of joints in the peduncle. 

 Figure i, G shows that in addition to the normal number there are two other 

 joints of the peduncle each a little longer than the last normal joint and sim- 

 ilar to it in shape; the flagellum is normal and so is the upper antenna. 



Orchestia chiliensis, var. gracilis nov. var. 



Locality. 



Masatierra, Portezuelo, »under stones. » 3. XII. 16. S. P. E. No. 32. 

 One male specimen only. 



This specimen measures about 13 mm. in length. It is a male with well 

 developed subchelate second gnathopods. The lower antennae and the 3rd 

 to 5th peraeopods are much longer and more slender than in typical specimens 

 of O. chiliensis. In this respect the animal resembles true terrestrial species 

 such as Parorchestia sylvicola from New Zealand and Parorchestia haivaiensis 

 from the Hawaiian Islands. The three pairs of pleopoda are, however, all well 

 developed, extending well beyond the side plates of their respective segments, 

 the third pair being about as long as the first. The first gnathopod (fig. 2, C) 

 is slightly more elongated than in 0. chiliensis but otherwise of quite similar 

 structure. The telson bears numerous lateral spinules as in O. chiliensis. The 

 second gnathopod (fig. 2, D) is not distinctive, the strong rounded tooth near 

 the base of the finger not being well developed, the rest of the palm is slightly 

 uneven, the finger regularly curved and fitting into a slight groove at the end 

 of the palm. There is nothing very characteristic about this gnathopod, but 

 it may be looked upon as a slight modification of the form usually found in 

 O. chiliensis. For the sake of comparison I give figures of the antennae (fig. 

 2 A, B), of the first and second gnathopods (figs. C, D) and of the fifth perae- 

 opod (fig. 2, E) which will render further description unnessary. 



I feel pretty confident that this specimen is to be looked upon as a modi- 

 fied descendant of O. chiliensis. There are no particulars given of the con- 

 ditions under which it is living except that it is found under stones in Porte- 

 zuelo. It was collected at a considerable height above the sea shore (590 m.) 

 and has become more adapted to terrestrial life than the forms described above 

 with the result that the appendages have increased in length, though the well 

 developed character of the pleopods shows that i thas not been so long adapted 

 to terrestrial conditions as the species of Parorchestia mentioned above. 



