On the Mo)iticuliporoids of the Cincinnati Group. 1 3 1 



those which are obscure. More especially do we believe this the 

 better course because of the uncertainty and unreliability, as well 

 as the difficulty of studying thin, microscopic sections.* 



The type species of the genus Monticulipora, D'Orb, has been 

 the subject of considerable discussion. Dr. Nicholson thinks that 

 D'Orbigny had before him at the time the description was made, 

 one of four species which, externally very similar, were, internally 

 very different. He concludes that a common form growing in 

 "thin undulated fronds, .... with its surface covered with 

 monticules, which are sometimes low and rounded, sometimes 

 conical, .sometimes elongated," should be considered as the type 

 and be called J/, iiiammi/lata.j Mr. Ulrich on the other hand + 

 considers that the form regarded by Nicholson as the type ot the 

 genus is really what collectors at Cincinnati have always called M. 

 fTotidosa, and that the true marjujiulata of D'Orbigny has been des- 

 cribed by Dr. Nicholson under the new name of fiwhsfa. It must 

 be confessed, however, that the selection of one is a matterof in- 

 dividual opinion, and one person is as likely to be right as another. 

 It is worthy of note, however, that the two species inammulata and 

 frondosa are easily separable upon a character which is revealed by 

 a rough fracture, as will be pointed out later on. 



The zoological position of the Monticuliporoids, is a question 

 which has been discussed from two sides, one party considering the 



*lt will be well in this place to give some idea of the manner of preparing- these thin 

 sections; this is as follows: In many cases three different sections are marie to study 

 the internal structure of any specimen. 'I'he'^e a.re caWed iano't-ntial , lotiffiiudhial nr 

 vertical, and transi'erse. In making tangential sections, the surface of the specimen is 

 g-rouud off just enough to get below the moaihs or apennres of the tubes or corallines, 

 cutting these at right angles with their long axes, care being taken to have the surface 

 perfectly level, and cut directly across the tubes. As most ot the Moiiticitlipom have a 

 more or less convex or undulating surface, some ot the tubes, ;'. r , the central ones on 

 the highest part, will unavoidably be cut lower down than some others. In consequence 

 of the undulating surface, some of the tubes are not cut directly across, but more or less 

 diagonally. After grinding, the surtace must be polished to free the section from 

 scratches, and it is then cemented, polished surface down, by means of balsam to a giass 

 slide. Then the other, free, side is rubbed down the same way, until the section is as 

 thin and transparent as it is possible lo make it and not destroy the internal structure. 

 This side is then polished in its turn, and then covered with a thin cover glass, or occa- 

 sionallv simply flowed with balsam; the former is the better. It is then ready for the 

 microscope. 



The process is the same in making other sections. The vertical section is cut in the 

 long direction of the tubes, from the central axis to the surface. As the corallitt-s are 

 seldom in straight, parallel lines, but are more or less curved, wrinkbd or undulating, 

 they are liable to be cut in one or more directions, so as to make it difficult to trace the 

 walls continuously from the base to the surface. 



The third kind, transverse, at exact right angles with the long axes of the corallites. 

 are sometimes made at various distances from the surface. 



The tabula;, or diaphragms, seldom pass in a perfectly horizontal direction across 

 the tubes from one side to the other. >-ome are diagonal, <:ome are curved more or less, 

 some form what Dr. Nicholson calls "lenticular vescicles." attached to only one wall of 

 the tube. In making tangential sections, some of these oblique or curved tabula are cut 

 away in the centre, leaving an apparent perforation in the middle of the tube. Others, 

 when cut away on one side leave a crescentric line in the tube, so that tangential sec- 

 tions of the sarne species may present very different appearances. 



fGenus Monticu., p. io8. JJ. C. S. N. H., v. 133. 



