30 



from that described by Mr. Bourne [mfra). — Dr. J. M uri e exhibited and 

 made remarks on the caudal end of the spine of a haddock with an arched 

 deformity, recalling what is recorded of the so-called hump-backed cod 

 [Morrhna macrocephala) . — Prof. P. M. Duncan read a paper on the jie- 

 rignathic girdle of the Echinoidea. The author maintained that as the struc- 

 tures which give attachment to the muscles that protrude and retract the jaws 

 of the Echinoidea (which are parts of the test surrounding the peristome 

 within) are not homologous in all the families of the group, therefore it is 

 unadvisable to retain the old name of »auricles«. He suggests to substitute 

 the term »perignathic girdle«. The girdle consists of processes usually united 

 above (though occasionally disconnected), and of »ridges« which connect the 

 processes on the side remote from the ambulacra. The ridges are modifica- 

 tions of the inter-radial plates, the processes developments from the ambula- 

 cral plates. In the Cidaridœ, the muscular attachments are all on discon- 

 nected ridges, and there are no processes. In the Temnopleuridse, Echinida?, 

 Echinometridse, and Diadematidae, the retractor muscles are attached to »pro- 

 cesses« which are growths of the poriferous portions of the ambulacral 

 plates ; and the protractor muscles and ligament of the radiais are attached 

 to the ridge which is developed on the inter-radial plates, and is united by 

 suture to the base of the »process«. In the Clypeastrida? there are discon- 

 nected growths which carry the jaws and have slight muscular attachments. 

 In Clypeaster there are ten processes, each arising from an ambulacral plate; 

 and there are no inter-radial structures like ridges. In Lagamim there are 

 five growths, each arising from a first inter-radial plate ; hence these are the 

 homologues of ridges. The Clypeastridse may thus be divided into two 

 groups^ on account of the presence of processes in one, and of the homolo- 

 gues of ridges in the other. — Prof. Moseley communicated a paper on the 

 anatomy of Sphœrotheriiim by Mr. Gilbert C. Bourne. The author mentioned 

 that while the general exterior features and specific distinctions of the genus 

 had been amply discussed, the internal structures had hitherto received scant 

 attention. Among other anatomical peculiarities he describes a well-defined 

 stridulating organ in the male. This consists of a prominent bolster-shaped 

 swelling on the postero-external edge of the second joint of the second pair 

 of copulatory appendages. The swelling occupies the entire mai'gin of the 

 joint, and shows a number of chitinous cross ridges and furrows. On the 

 opposite interior surface of the last tergite are chitinous points. The former 

 rasp-like organ of the second accessory appendages when rubbed rapidly 

 against the latter produce a shrill note resembling that emitted by the house 

 cricket. A true auditory organ exists in the antennary fossa beneath the eye. 

 The tracheal system is unlike the majority of that of the Diplopoda, rather 

 resembling that of Chilopoda and Insecta, though differing in the branched 

 spiral filament not taking origin directly from the stigmata themselves. It 

 appears that the tracheae of Splicerotherimn are a transition from those of the 

 Julus type to those of the ScolojDendra type. It would thus seem that the 

 character of the trachea}, the curved alimentary tract, the numerous chitinous 

 pieces composing each segment, and the presence of a special hearing organ 

 on the head, mark off the family Glomeridae (to which Sphcerotherium belongs) 

 very sharply from the other families of the Diplopoda. — Prof. Moseley 

 afterwards read extracts of letters from Mr. G. C. Bourne, who is now in 

 the Chagos Archipelago, and from Mr. Sydney Hickson in the Celebes (Ox- 



