117 



HOMARUS. 



HOMOLID^E. 



113 



Lobsters (Humarus) from the Crawfishes (Astacus), and to combine the 

 genera Attacus, Homarus, and Nephropi in one small group, which he 

 designates as the family of the Astacia.ns(Aitacidte). These he considers 

 as forming the passage between the Cuirassed Macrurous Crustaceans 

 and the Salicoques, or Shrimps, but as differing sufficiently to require 

 separation. In the general form of the body the Astacidce approximate 

 very nearly to the Salicoques, but they have not, he remarks, like 

 them, branchiae composed of lamina; piled one on another ; these 

 organs being formed by an assemblage of small cylinders more or less 

 long, and brush-like, as in the greater part of the Cuirassed Macrura, 

 which the Astacians also resemble in the hardness of their tegumentary 

 skeleton ; but their sternum is not enlarged into a plastron, and the 

 nervous ganglions corresponding with the two thoracic tings are 

 distant, and united by rather long double cords. 



The body of the Astacians is elongated and a little compressed ; 

 the abdomen is very large, but at the same time less developed in 

 proportion to the thorax than it is in the Shrimps. The carapace 

 terminates anteriorly by a moderate rostrum, which overhangs the 

 base of the ocular peduncles. The antennae are inserted nearly on 

 the same transversal line ; those of the first pair are of moderate 

 length, their peduncle is straight, and their terminal filaments two in 

 number. The external or second pair are much longer, and their 

 peduncle is furnished above with a moreable plate, which is analogous 

 to the ifiinifonn appendage in the Paguri, as well as to a similar but 

 much larger plate which is found in the Salicoques. In the Astacians 

 this appendage is hastifonn, and never entirely covers the last pedun- 

 cular joint situated below, and it is even rudimentary. The buccal 

 apparatus presents nothing remarkable ; the external jaw-feet are 

 elongated, but bent back upon the mouth ; their second joint is much 

 larger than those which succeed, and they do not assist in locomotion. 

 The first pair of feet are very large, and terminated by a large diduc- 

 tylous claw ; the last four pairs are of moderate length, and nearly of 

 the same general form, excepting that the secor^J and third pairs are 

 provided with a small didactylous claw, and that the last four are 

 monodactylous. The abdomen is nearly of the same size throughout, 

 and presents on each side a lamellar prolongation, which descends so 

 as to incase more or less completely the base of the false feet. The 

 last segment is very wide, and forms, with the two plates of each of 

 the appendages of the sixth ring, a great caudal fin, all the pieces of 

 which are nearly of the same length. The external plate of this fin 

 has a transverse joint towards its posterior third part. The false 

 natatory feet are elongated ; in the male the first pair are styliform, 

 nearly as in the Brachyura, while the others are terminated by two 

 large foliaceous plates with ciliated borders, a condition which belongs 

 to the whole of these feet in the female. The branchiic amount to 

 twenty on each side. They are disposed in three rows, so as to form 

 vertical bundles separated by fiabelliform appendages, fixed to the 

 base of the feet. These last-mentioned appendages are very large, and 

 are only wanting in the posterior feet. 



This family corresponds to the genus Astatuiot Fabricius ; and 

 M. Milne- Edwards, adopting the division established by Dr. Leach in 

 founding his genus Nephropi, further separates the Crawfishes pro- 

 perly so called, from the true Lobsters thus : 



Rostrum depressed, and armed with 

 one tooth at most on each side. Last tho- 

 racic ring moveable. 



f- Eyes spherical Last " 



ring of the thorax 

 Rostrum straight, soldered to the pre- 

 and armed with ' ceding. 



Aitacut (Crawfishes). 



Jfomariu (Lobsters). 



> ffephrops. 



many teeth on each Eyes reniform. Last 

 side. ring of the thorax 



preserving a little 



mobility. J 



But the separation thus further carried out by M. Milne-Edwards 

 does not depend on external distinctions only ; for there are great 

 differences in the conformation of the internal organs of generation 

 and digestion, as compared with that of those essential parts of the 

 animal economy in the other Ailacida. Thus M. Milne-Edwards 

 remarks, that in the Crawfishes the duodenal portion of the intestine 

 presents on its internal surface a great number of small villosities, 

 and is not clearly separated from the rectum, which is smooth inter- 

 nally ; while in Homarut the duodenum is smooth within, the rectum 

 is plaited internally, and there exists between these two parts of the 

 digestive tube a kind of circular valvule ; the posterior ciucal append- 

 age of the intestine, which is seen at the extremity of the duodenum 

 of the true Lobsters, is wanting in the Crawfishes. The liver is com- 

 posed in the Crawfishes of small csecal tubes, which are comparatively 

 much more elongated, and its anterior lobes are less developed ; the 

 testicle is very small, and is composed of three lobes, whence spring 

 the very lom; and tortuous deferent vessels, whilst in the true Lobsters 

 these secreting organs are very much elongated, extending from the 

 head into the abdomen, presenting no mesial lobe, but a simple com- 

 missure, and only giving rise to very short deferent canals. 



The Aitaci, which are all fiuviatile, consist of the species A. fluvici- 

 tilit [ASTACUH], A. Bartonii, A. affinit, A, Autlralatientii, A. Chilmris, 

 and A. landingii(l). 



The lluntM-i, which are all marine, consist of the species //. iiul- 

 garis, the Common Lobster [ASTACUS], H. Americanus, with its 

 immense claws, and H. Capensis, according to M. Edwards, who con- 

 siders the Astacus scaber of Fabricius as identical with H. Capensis. 

 The species A. cazrulescens, A. fulgens, A. fidvus, are unknown to 

 M. Edwards, and considered doubtful by Latreille. 



Nephrops (Leach). Body more elongated than that of the Craw- 

 fishes ; rostrum slender and rather long, armed with lateral teeth 

 like that of ffomarus. Eyes large and reniform. Lamellar appendage 

 of the external antenna! wide, and long enough to extend beyond the 

 peduncle situated below. Feet, first pair long and prismatic ; succeed- 

 ing pairs with a compressed mantis. Nothing remarkable either ill 

 the abdomen or in the buccal appendages. Branchiae disposed as in 

 Ifvmarus. 



N. Norvegicus, the Norway Lobster, Cancer Nonegicus of Linnaeus, 

 is occasionally taken in the seas around the British Islands. It is one 

 of the most beautiful of -the larger Macroura. Its general colour is 

 pale-flesh, rather darker in parts ; the pubescence is light brown. It 

 is generally considered a northern species, but Mr. Bell says he has 

 received specimens from the Mediterranean. It is found on the coast 

 of Norway in large quantities, and is also frequently taken on the 

 coasts of Scotland, and sold in the Edinburgh and other markets. It 

 is taken in Dublin Bay, and is very common in the Dublin markets. 

 It may also be occasionally seen in the London shops. It is said to 

 be the most delicate-flavoured of all the Crustacea. Forms of the 

 A star ill a' are found fossil. [CRUSTACEA.] 



Norway Lobster (Xephropt Korvegicvs). 



HOME. [ 



HOMELYN. 



HOMOCERCAL. Fishes with symmetrical forms of tails are 

 thus named by M. Agassiz, in contradistinction to Heterocercal. 

 [HETEROCEUCAL.] 



HOMOLA. [HoMOLio^.1 



HO'MOLID^E, Jfomola Tribe. The Homolians, according to the 

 system of M. Milne-Edwards, are the second tribe of the Apterurous 

 family of the Anomurous Crustaceans, and their place is between the 

 Dromians and the Raninians. 



The carapace is spiny, and armed with a rostrum. Internal pair of 

 antennae without a pit, and incapable of being bent back upon the 

 front. Jaw-feet pediform. Feet of the second, third, and fourth pain 

 very long ; fifth pair very short, and of no service in progression. 

 Sternal plastron enlarged. Claw terminating the anterior feet, com- 

 posed of two fingers in the ordinary form. Tarsi of the three 

 following feet styliform. Posterior feet more or less completely 

 prehensile. 



