

'*, 



■ 1 



Dublin Microscopical Club. 215 



Sections of Leaves of Abies Pattoniana.— Dr. M'Nab exhibited 

 sections of the leaves of the specimens named Abies Pattoniana, 

 in the museum and herbarium of the Royal Botanic Gardens, 

 Edinburgh. These were Cascade-Mountain specimens (Jeffreys, 

 No. 430), identical with the plant described by Mr. Andrew Murray, 

 ia 1855, as Abies Hookeriana, and quite distinct from Jeffreys's 

 Mount-Baker plant, sent by him under the manuscript name of 

 Abies Paltonii. 



Ditrema jlavum, Archer, occurring in Scotland. — Mr. Archer 

 showed the test of Ditrema Jlavum, which he had met with in 

 Scotland. It is curious that neither the present form nor Amphi- 

 trema Wrightianum has seemingly been met with out of the United 

 Kingdom, whilst Dip>Jop)hrys Archeri, the other known aruphitre- 

 niatous thalamiphore, has now been encountered in many places ; 

 but the two forms in question are certainly to be accounted as 

 amongst the rarities. 



Odontophore of Fusus antiquum. — Prof. Mackintosh exhibited 

 the odontophore of Fusus antiquus, showing also, for the 6ake of 

 contrast, that of Buccinum undatum. 



December 15, 1881. 



Apatite in Micaceous Diorite. — Prof. Hull, F.R.S., exhibited a 

 thin section of a micaceous diorite from a dyke half a mile east of 

 Streamstown, near Clifden, Connemara, remarkable for the number 

 I and size of the crystals of apatite which it contains. The rock 



consists of a felspathic crystalline base, in which are enclosed nume- 

 rous well-formed crystals of hornblende in short prisms, a few flakes 

 of mica, peeudomorphs after olivine, and crystalline grains of mag- 

 netite. The association of these minerals causes the section to pre- 

 sent a very beautiful and varied aspect under polarized light. 



In addition to the above, the rock is traversed in all directions 

 by numerous long slender prisms of apatite, which in some cases 

 show pyramidal terminations, and, when cut transversely by the 

 plane of the section, hexagonal forms. In two or three instances 

 sections are shown nearly perpendicular to the principal axis, and 

 when polarized appear dark with crossed nicoLs. The determination 

 of these prisms, both as regards form and optical properties, is 

 therefore complete ; and it may be supposed that the rock from 

 'which the section is taken is very rich in phosphate of lime. 



Cosmarium platyisthmum, n. s. — Mr. Archer exhibited a new Cos- 

 marium of minute size, but not amongst the most minute, of a quite 

 unique form ; in general outline in front or broad view much re- 

 sembling, say, a section of a double (railway) " rail," or, say, that of a 

 pulley — that is to say, the isthmus very broad and comparatively 

 long (the body of the " pulley "). Thus the " isthmus n makes up 

 a great porportion of the whole Cosmarium; the semicells are 

 ellintie. muoh hrnartar than hiVh (forming the rim or external pro- 



