40 Mr. C. Spence Bate on the Homologies of the Carapace 



of the carapace of Crustacea had induced him to arrive at, are iu 

 some of the most important points anticipated in the work of 

 the United States' Exploring Expedition. 



But since they have been arrived at by independent research, 

 the regret with which the author found his deductions forestalled, 

 are to a considerable extent removed by the important testimony 

 of so learned and correct a naturalist as Mr. Dana. The follow- 

 ing two sentences are taken from the first volume of that author ; 

 the italics being in the original text : — 



" We are therefore led to believe, that the so-called epimei^als, 

 or ventral pieces of the carapax, «re in fact the posterior exten- 

 sions of the mandibular segment J" (Page 27.) 



Again — 



" . . . . Milne-Edwards thus makes the larger part of the 

 carapax epimeral in character. 



" Excepting that we consider what is here called epimeral, the 

 mandibular segment, we agree with Edwards, for the most part, 

 in the above-mentioned deduction ; so that while the mandibular 

 segment is confined to the ventral pieces of the Brachyural cara- 

 pax, it constitutes its posterior half in MacrouraJ' (Page 32.) 



The author also has had the opportunity at the British Mu- 

 seum of seeing the plates in Kroyer's great work on the Natural 

 History of Scandinavia, where he finds the carapace of Cuma 

 Rathkii (Kroycr) (the Alauna rostrata of Goodsir) is figured 

 with the so-called rostrum separated from the antennal region, 

 as drawn and described in this paper. 



The Anterior or Internal Antennce. 



These organs are borne by the second ring, and supplied with 

 nerves from the cephalic ganglion. 



The anterior antenna is evidently of importance to the animal, 

 and is always present in aquatic Crustacea : as a general law it 

 consists of an articulated peduncle of three joints, which I believe 

 I am correct iu asserting, unlike those of the external antenna, 

 are never anchylosed together or with the carapace, and a 

 terminating filament, which is generally double, often treble, 

 but 1 believe never single, above the Amphipoda. This appen- 

 dage is various as well as unequal in length, and in every species 

 that I have examined, whether in Brachyura, Macroura, Am- 

 phipod or Isopod, will invariably be found furnished, in addition 

 to the small hairs common to otlicr parts of the animal, with 

 long, delicate, membranous cilia, in form varying in genera and 

 species; they arc always larger than the ordinary hairs, but 

 much more delicate in structure. These vary in number and 

 in thickness of clusters, but, as far as my experience goes, are 

 invariably present on the upper antenna. 



