292 Zoological Society : — 



paper last quoted, as by previous authors ; and the object of this 

 note is to direct attention to the support which the extended view 

 aro-ued for by me in the paper above referred to, viz. that the finer 

 markings also correspond to depressions, derives from analogy. 



The structure of the Diatomaceae, and their modes of reproduc- 

 tion, are, as is well known, remarkable; — so much so, that these 

 or'^anisms have been claimed by botanists as members of the vege- 

 table, and by zoologists as belonging to the animal kingdom. The 

 preponderance of evidence is decidedly in favour of their vegetable 

 nature ; but, be this as it may, they must all be classed together, — 

 they form a perfectly natural family. Hence we have a strong argu- 

 ment in favour of the markings upon their valves being identical, 

 and as these are evidently dejjressions in the genera and species with 

 coarsely marked valves {Isthmiu, &c.), we should e.\pect from ana- 

 logy that the same would apply to those with finer markings. And 

 this view receives further support, from the fact, that under varied 

 methods of illumination, corresponding appearances are presented 

 by the markings when viewed by the microscope, from those which 

 are very large, as in Isthmia, through those of moderate and small 

 size, as in the species of Coscinodiscus, down to those in which 

 they are extremely minute, as in the species of Gyrosigma, &c. The 

 angular (triangular or quadrangular) appearance assumed by the 

 markings, arises from the light transmitted through the valves being 

 unequally oblique. This may be readily shown in the more coarsely 

 marked valves {Isthmia, Coscinodiscus), which present the true 

 structural appearance when the hght is reflected by the mirror in 

 its ordinary position, and the spurious angular appearance when the 

 light is rendered oblique by moving the mirror to one side. 



ZOOLOGICAL SOCIETY. 



December 13, 18.o3.— R. C. Griffith, Esq., in the Chair. 



Descriptions of New Species of Bucconid^. 

 By Philip Lutley Sclater, F.Z.S. 



1 . Bucco RADIATITS, Sclater. B. sujjra dare ferrugineus, nigra 

 iransversim radiatns ; nucha et dorso sumnw pcene omiiino 

 nigris ; corpore subtus et torque cervicali supra pallide fulces- 

 centi-albis ; capitis lateribus, pectore et venti'is lateribus lineis 

 nigris transversim radiatis ; loris, gula, ventre medio crissoque 

 albis ; pedibus nigris ; rostro plumbeo. 



Long, tota 8*0 ; alee, 3--4 ; caudse, 3-0. 



JIab. in Nova Grenada. Mus. Britannico. 



Obs. B. chacuru affinis, sed subtus radiatus et rostro plumbeo nee 

 Tubro ; maculis auricularibus nuUis. 



-2. Bucco STRiATiPECTUS, Sclater. B. corpore sup)ra nigrescente, 

 alis caudaque mugis brunnescentibus, oninino rufescente trans- 

 versim striatis ; capite nigra fere immaculato ; inento alba ; 

 gvtture to to et coUo undique fulvo-rujis ; pectore et ventris 



