250 LOPHOBRANCHII. 



Order IV— LOPHOBRANCHII, Cuvier. 



Fishes possessing a dermal, segmental skeleton, and the opercular pieces 

 reduced to a single plate. Gill-openings small : gills consisting of small and 

 rounded tufts attached to the branchial arches. Muscular system very slightly 

 developed. Snout produced : mouth terminal, but small. Teeth absent. Air- 

 bladder stated to be destitute of a pneumatic duct (but it is present in some 

 forms, as Syngnathus acus). 



The fishes "which belong to this order, and popularly known as pipe-fishes and 

 sea-horses, normally swim in a vertical position, the dorsal fin being the principal 

 propeller, and which while in motion is rapidly undulated from end to end. The 

 tail fin, remarks Gray, seems to be used rather as a foot than as an organ of pro- 

 pulsion, and when the species with a rayed caudal fin employs this part, it expands 

 the rays giving the end of the tail the appearance of a webbed foot. The action 

 of the mouth is similar to that of a common syringe, due to the dilatation of the 

 throat ; the water enters the tubular-formed mouth, while it is ejected again by 

 compressing and so emptying the cavity. 



As regards propagating their species Professor Canestrini considered that a 

 coitus occurs, when the ova are transferred from the female to the male, the latter 

 fecundating them after they have entered the ovigerous sac. Kaup remarked that 

 in most of the species the males perform the function of hatching the eggs, which 

 for that purpose are deposited, up to the time of the evolution of the young, either 

 between the ventrals (Sulenostomus'), or in tail pouches {Hippocampus'), or in 

 pouches on the breast and belly (DoryrkampJius) , or in rows on the breast and 

 belly (Nerophis), and are thus carried about by the fish. Dr. Giinther in his 

 observation on Solenostoma cyanopterum remarks, " Kaup states that in the males 

 of Solenostoma paradoxiom the egg pouch is formed by the union of the inner 

 edge of the ventrals to the skin of the belly, and that in the females the ventrals 

 are free as in other fish. All the specimens from Zanzibar which have been 

 examined have the ventrals attached to the skin of the belly, and all of them are 

 females : so that if the first part of Dr. Kaup's remarks prove to be true, both 

 sexes in this species carry eggs." Canestrini observed a caudal fin in young 

 Hippocampi, and Pries the rudiments of fins in the young of Nerophis. 



The fishes of this order have been divided into two families : — 



1. Syngnathidce. — Small gill-openings : one dorsal fin, no ventral, and some of 

 the other fins may be absent. 



2. SolenostomidcB. — Wide gill-openings : two dorsal fins, and the other fins well 

 developed. 



Family I-SYNGNATHID^. 



Gill-openings small and situated at the posterior superior angle of the gill- 

 cover. A single dorsal fin. Ventrals and occasionally one or more of the other 

 fins absent. 



Along our shores these fishes are mostly found on Zostria beds, from low water- 

 mark to deep water. 



Mr. Andrews says all British forms are common in harbours and estuaries of 

 S.W. coast of Ireland — 8. acus and S. typhle. They pass ova thus : " In shoal 

 water or a low tide these fish may sometimes be seen in pairs, side by side, appa- 

 rently stationary on some rocky stone. At this time the ova — the capsules but 

 imperfectly matured — are liberated from the female, and received into the 

 abdominal sac of the male, the male fish having the power of expanding the 

 lappings of the sac and attaching the ova by a highly viscid or glutinous secretion. 

 As the process of maturation advances, the capsules of the ova enlarge, forming 

 hemispherical depressions in the sac, and eventually the pouch is forced open by 

 the full development of the ova and the extrication of the young." — Zool. xviii, 

 1800, p. 7053. 



