ICHTHYOLOGY. 



211 



Introduc- B. The bones of the Splanchno-skeleton constitute in the 

 tion. skull, — a. The ear-capsule or petrosal and otolite. b. The 

 Osteology, eye-capsule or sclerotic and pedicle, c. The nose-capsule 

 ^"^"V"^ or ethmoid and turbinal. d. The branchial arches. 



c. The bones of the Dermo-skeleton belonging to the 

 skull are, — a. Supra-temporals. (3. Supra-orbitals. y. Sub- 

 orbitals. S. Labials. 



A. I. The Epencephalic arch consists of the basi-occipital, 

 on which there is an excavation similar to one on the first 

 abdominal vertebra, and with which it is articulated through 

 the intervention of a capsule filled with jelly. This articular 

 cup varies from a deep conical excavation common to many 

 fish, to the almost flat surface which it presents in the 

 Holibut, and, what is extremely rare, to a convex surface as 

 in Fislularia. In the Carp, the imder surface of the basi- 

 occipital forms a broad triangular plate, on which there is 

 planted the large upper pharyngeal grinding tooth. This 

 bone is the centrum of the arch. The ex-occipitals or 

 neurapophyses are articulated one on each side to the basi- 

 occipital, and, in most fishes, they expand on the upper 

 surface of that bone, so as to meet and support the medul- 

 lary column ; but sometimes a space is left between them, as 

 in the Lepidosiren, ^vhose basi-occipital completes ^e fora- 

 men magnum of the skull. The par-occipitah form the 

 upper lateral curve of the arch, and are wedged in between 

 the ex-occipitals and the supra-occipital^ which forms the 

 key of the arch, and raises a strong compressed crest-like 

 spine from the whole length of its mesial line ; a transverse 

 supra-occipital ridge coming from each side of the base of 

 this spine runs outwards laterally to the external angles of 

 the bone. The supra-occipital is separated fi-om the fron- 

 tals in the Salnionoid, Clupeoid, Cyprinoid, Muraenoid, and 

 Salamandroid families; but, in the majority of fishes, it runs 

 forward between the parietals to join the frontals. In 

 Lepidosteus, it is itself divided by a median suture. In 

 greatly compressed skulls, the occipital spine is usually very 

 lofty ; and, in Epidppus, its peripheral edge swells out like 

 the crest of a helmet, whence the fish is named the Light- 

 horseman. In depressed skulls, on the contrary, the spine 

 is low and merely projects backwards, as in the Pike and 

 Salmon ; while in some it is wholly obsolete, as in the 

 flat-headed Retnora. In the unsymmetrical skulls of the 

 Pleuronectidce, it is pushed from its usual place by the par- 

 occipitals, and one of its lateral plates is not developed. In 



broad depressed skulls the par-occipital forms a strong Introduc- 

 crest, and exceeds the ex-occipital in size. In Si/nodus, tion. 

 C'allicthi/s, and Heterohraitchus, the par-occipital is visible Osteology, 

 only at the back part, not on the upper aspect of the skull. ^— v'^" 

 The outer projecting process supports the upper fork of the 

 first piece of the scapular arch, sometimes, as in Ephippus, 

 by a distinct articular cavity. 



The members of the occipital vertebrae are the parts 

 which are commonly most completely ossified, and in 

 Polypterus they are anchylosed into one piece. Both the 

 par-occipital and the ex-occipital are excavated for lodging 

 the posterior and external semicircular canal of the enor- 

 mous internal organ of hearing, and the acoustic capsule, 

 or petrous bone, as it is named from its hardness, is interca- 

 lated between the par-occipitals and the ali-sphenoids. In 

 the Carp, a chain of ossicles connects the air-bladder with 

 the organ of hearing. 



II. The Mesencephalic arch has for its centrum the basi- 

 sphenoid, which is always connate with the pre-sphenoid 

 (belonging to the next arch), and forms with it a long sub- 

 triedral bone (basi-pre-sphenoid), usually split or forked 

 posteriorly, more or less expanded beneath the cranial 

 cavity, and then continued forwards, along the base of the 

 inter-orbital space to near the fore part of the roof of the 

 mouth, where it terminates by a cavity that receives the 

 pointed end of the vomer. This end of the basi-pre- 

 sphenoid is twisted up in the Pleuronectidce. The longer 

 and narrower the skull, the longer in general is the basi- 

 pre-sphenoid. Rarely does any portion of it show on the 

 floor of the cranial cavity, but in the Cod a small part 

 supports the pituitary sac ; in Fistularia a transverse ridge 

 of it appears within the cranial cavity, and in some other 

 fishes it sends a small process up on each side. The ali- 

 sphenoids or neurapophyses of this arch are articulated 

 firmly to the sides of the basi-sphenoid, their bases usually 

 expanding over this bone so as to meet and form part of 

 the floor of the cranial cavity. In some fishes, as in the 

 perch and carp, these expanded plates of the bases are 

 raised from the basi-sphenoid so as to form a sub-cranial 

 canal which exists in the Salmonoids, Sparoids, Scombe- 

 roids, and is very remarkable in Ephippus, and most fishes 

 that have lofty compressed skulls. It exists in some 

 Clupeoids, but not in the Salamandroid fishes. In deep 

 and compressed skulls the ali-sphenoids are narrow and 



Ectopterygoid 



Malar 



Squamosal 



SPLANCHNO-SKELETON. 



CAPSULES OF ORGANS OF SENSE INTERCALATED WITH THE 



Petrosal 1 , 



n* . 1 1 Acoustic 



Otosteal J 



Ethmoid and Ethmo-turbinal 



Turbinal 



CRANIAL BONES. 



Kocher 



13. 



Spheno'ide anterieur 15. 



Nasal 20. 



BRANCHIAL ARCHES. 

 Hypo-branchial Piece interne de partie in- 



ferieure de Varceau bran- 

 chiate 57. 

 Cerato-branchial Piece externe de partie in- 



ferieure de rarceau bran- 

 chiale 58. 



Partie sup^rieure de I'arceau 



Epi-branchial 

 Pharyngo-branchial 



branchiale 

 Os pharyngien superieur 



DERMO-SKELETON. 

 Supra-orbital scale-bone Suroibitaire 



Supra-temporal scale-bone Sur. temporal 



Sub-orbital scale-bones Sous-orbitaires 



Lachrymal Lachrymal 



Labial Labial 



ENDO-AND EXO-siELBTON OF THE BODY AND TAIL. 

 Abdominal vertebraj Vertebres abdominales 



Caudal vertebraj Vertebres caudales 



61. 

 62. 



72. 

 19. 

 19. 



67. 



68. 

 69. 



Centrum 



Neurapophysis 



Neural spine 



Interneural spine 



Derrao-neural spine 



Zygapophyses 



Parapophyses 



Haemal canal 



Hceraal spine 



Interhgemal spine 



Do., aggregated at base of 



caudal fin 

 Dermo-hEemal spine 



Spinous rays 



Soft-jointed or branching rays 



Pleurapophysis or rib 



Epipleural spine 



Ventral fins, being the ha?ma- 

 pophysis with diverging 

 appet'idage of the last ab- 

 dominal vertebra 



Pubic bone in fishes ; the re- 

 presentatives of the femoral, 

 tibial, and tarsal bones, are 

 wanting 



Metatarso-plialangeal jointed 

 rays 



Corps du vertebre 67. 68. 69. 



Partie annulaire 



Apophyse epineuse c. 



Interepineux 74. 



Rayons dorsales 75. 



Apophyses articulaires 



Apophyses transverses 



Anneau inferieur 



Apophyse epineux inferieur 



Interepineux 6. 



Plaque triangulaire et ver- 

 ticale 70. 



Rayon de I'anale et du cau- 

 dal inferieur 78. 



Eayons epineux ou aiguil- 

 leus 75. 



Rayons articules, mous ou 

 branchus 71. 75-82. 



C6te 72. 



Appendice or stylet 73. 



Nageoires ventrales abdomi- 

 naux et subbrachiens. 



Un seul OS representant 

 I'os innomine, la cuisse, 

 la jambe, et le tarse 80. 



Rayons mous du nageoire 

 ventrale 82, 



