338 LIEUT. ANNESLEY ON GONODACTYLUS CHIRAGRA. [June 12, 



which, similarly to that on the dorsal outline of the skeleton, unites 

 the extremities of the interhaemals, extending from the end of the 

 anal to the pubic bones, and forming a complete but feeble ring 

 round and supporting the abdominal cavity. The pubic bones are 

 very short and coalesced, but slightly divergent behind, so as to 

 leave a narrow opening for the vent, which can be entirely closed by 

 the rudimentary and coalesced but ossified ventral fins, which serve 

 in this fish as a sphincter ani. 



The formula of fin-rays of this specimen are: — D. 13. A. 14. 

 C. 7+16 + 6. P. 15. 



4. Notes on the Habits of Gonodactylus chiragra. By Lieut. 

 O. F. T. Annesley, E.A. (Communicated by Dr. J. E. 

 Gray.) 



In May 1865, while stationed at Aden, I caught by a small hand- 

 dredge in a rock-pool an animal which I have since learnt is most 

 probably the " Gonodactylus chiragra," and for rather more than a 

 month I kept it, sometimes in a small tumbler, sometimes in a large 

 glass lamp, one of those which are occasionally used in halls, hanging 

 from the ceiling, and which when arranged form by no means a bad 

 aquarium. 



The colour of the animal, which was of a brownish yellow, has 

 greatly faded since its death. 



Perhaps what strikes one most is the two curious prehensile claws 

 with which the creature is provided. These are, I believe, used as 

 instruments of defence and offence, and are really most powerful 

 weapons. The animal seems to possess the power of darting them for- 

 ward with very great force ; and so beautifully are they constructed 

 that they appear never to suffer any injury, however hard may be 

 the substance against which they are driven. 



I have not forgotten how I first became acquainted with the fierce 

 propensities of the animal. I was moving one of the objects in the 

 aquarium with a long pencil ; in doing so I passed the pencil along 

 the bottom near the animal, which, without further provocation, 

 darted at it, nearly striking it out of my hand and astonishing me 

 not a little. And afterwards, whenever the pencil was moved towards 

 it, the animal invariably attacked it furiously ; in fact I think his 

 temper grew worse from our continually provoking him. 



Frequently when sitting at the end of the room I have heard 

 repeated knocks against the sides of the glass, occasioned by the 

 attacks of this animal against the harmless Ophiuri, who, when tra- 

 velling round the sides of the aquarium, inadvertently touched him 

 with one of their curious rays, which, though composed of hard cal- 

 careous matter, were always severed by a single blow from the claw 

 of the Gonodactylus. 



For the sake of experiment I enclosed an Ophiurus (each of whose 

 rays measured about 4 inches) and the animal in a tumbler, when the 



