On a Group of the Aplysiidie. 403 



mandibles; /./., lower lip ; inx. 1, one of the lirst maxillte, and spines 

 of the outer plate of the other more highly nmg'nified ; mxp., maxil- 

 lipeds; i^w. 1, Hr!<t frnathopod; yw. 2, second gnat hopud ; ;>?7^. 1, 3, 4,o, 

 first, third, fourth, and fifth peroeopods ; ur. 1, 2, 3, first, second, and 

 third uropods ; T, telson. 



The mouth-organs and parts of the pleon are much more highly magnihed 

 than the antenna) and limbs. 



Plate XV. A. 



Detttella Mat/en', 



Lateral view of the female above, and of the male below, the natural 

 size of the male being indicated by a line on the right. 



OS., the mouth-organs of the male specimen viewed laterally in situ. The 

 palp of the mandible is seen overtopping the upper lip ; the lower 

 lip can be perceived almost edgewise below the molar tubercle of 

 the mandible and above the palp of the first maxilla ; between the 

 latter and the prominent palp of the maxilliped are discerned the 

 two plates of the second maxilla. 



/.»'., lower lip; ?«.r. 1 , first maxilla ; ?;i.r. 2, second maxilla; w?.r/7., maxilli- 

 peds ; (/n. 1, first gnathopod. This group is taken from a specimen 

 smaller than either the male or female specimen figured on the plate. 



a.s., upper antenna; a.i., lower antenna; ffn.l, first gnathopod; y«. 2, 

 second gnathopod; i^rp.l, 2, 3, 5, first, second, third, and fifth 

 perseopoQs. 



The parts of the female are distinguisiied by the sign $ , of the male 

 bv the sign cJ . 



XLVII. — On a Group of the Aplysiida, toith Description of 

 a new Species. 13j J. Gilchrist, Ph.D., &c. 



[Plate XVIII.] 



'I'he following description of a small group of Aplysias is a 

 contribution to an account of the collection of Tectibranchs 

 in the British Museum (Natural History). This collection 

 contains a great number and variety of forms from the 

 PaciMc, Atlantic, and Indian Oceans, and illustrates very 

 forcibly what could be done if a systematic search for these 

 animals were made in almost any unexplored region. Owing 

 to careful preservation and a liberal supply of spirit some of 

 the specimens are in a good state of preservation and sufficient 

 for purposes of identification. 



The small group to be considered here is represented by 

 half a dozen specimens, more especially by Aplysia piperata 

 (Smith), from Thursday Island, Torres Straits ('Alert' 



