Mr. J. D. Macdonald on the Affinities of the Gasteropoda. 405 



" Siphonaria appears to enjoy the power of breathing in both 

 air and water with equal facility, and on examination, we find the 

 respiratory surface so constituted as to afford a ready explanation of 

 the fact. Thus, in connexion with a narrow, combed, or rather 

 transversely plaited gill, numerous vessels ramify extensively, and 

 anastomose freely upon the roof of the respiratory chamber. The 

 mouth is armed with lateral labial plates, and the lingual dentition is 

 not unlike that of Amphibola, to which genus it is further related by 

 the absence of tentacula, and the general configuration of its head. 



"Amphibola exhibits a close relationship to the Pidmonifera in many 

 essential anatomical points, but it has a veritable combed gill, which, 

 arising from a deep recess on the left side of the branchial chamber, 

 and thence passing obliquely forwards towards the right side, termi- 

 nates in a pointed extremity, in front of which there is a small 

 glandular body, probably a renal organ. The margin of the mantle 

 may be traced continuously round the neck and the base of the foot, 

 being attached in its entire extent, with the exception of a small 

 portion which arches over a narrow respiratory opening on the 

 right side of the nape. The lingual sac is small, lilve a csecal process 

 appended to the antero-inferior part of the cesoj)hagus. The dental 

 organs present a pavement of narrow basal plates with very long and 

 gently curved cusps. The teeth of the central series are much larger 

 than the rest, and exhibit a remarkable conformation ; thus a rounded 

 process projects in the middle and several minute denticulations arm 

 its base on either side. I have not succeeded in detecting either 

 lingual cartilages or labial plates in my spirit-preserved specimens, 

 and but for the support furnished b}' analogy, I would incline to the 

 belief that they are absent in the present case. 



"The remark made by Mr. Woodward in his very valuable little 

 work the ' jSIanual of JMolhisca,' that the anomalous genus Amphibola 

 lias an unusually broad tongue armed with teeth similar to those of the 

 Sua:!, is not quite correct. The misconception most probably origi- 

 nated in the inspection of a pre])aration belonging to Mr. AVikon 

 of Gloucester, and from which Mr. Woodward's figure has been 

 taken, as ' part of the tongue of Amphibola avellana ; ' but Iiaving 

 myself dissected several specimens of this very species obtained at 

 New Zealand, I am satisfied that Mr. Vv^'ilton's preparation has been 

 by some accident improperly named. 



"The general scheme of the genei'ative system in Amphibola 

 corresponds very closely with that of Helix, Bulimiis, and such Pul- 

 monifera. The ovarium is imbedded in the liver near the summit 

 of its spiral turns, and a small convoluted oviduct leads downwards 

 and forwards along its inner or concave side. The testis lies con- 

 siderably in advance of the ovary ; the intromittent organ forms a 

 prominence in the floor of the respiratory chamber, and finally tht; 

 generative orifices open on the right side." 



