HILL: GEOLOGY OF JAMAICA. 241 



nen Sternreihen bedeckt, die einen Querdurchmesser von 2-3 Millim. besitzen. 

 Sie werden durch wenig tiefe Zwischenfelder getrennt, die in der Kegel eben 

 so breit sind als die Thaler und nur stellenweise, besonders an Punkten 

 stiirkerer Kriimmung, sich mehr ausbreiten oder im Gegentbeile verengem. 

 Sie sind mit gedrangten, wenig ungleicben Rippchen besetzt." 



The columella is practically the same as in D. confer ticostata^ sometimes 

 appearing somewhat spongy. " Die Septallamellen sind gedrangt und diinn, 

 an Dicke wenig ungleich. Zwischen zwei langere findet man jedoch fast 

 regelmassig eine viel kiirzere eingeschoben. Die langereu verdicken sich in 

 der Nahe der Axe zu einem starken Knotchen, das sich mit den benachbarten 

 verbindet. Die dadurch entstehende Knotchenreihe wird von der Axenlamelle 

 durch eine ziemlicb tiefe Furche geschieden. In der Lange eines Centimeters 

 zahlt man etwa 44 Septallamellen." 



From this description three points of difference become apparent: 1st, the 

 valleys in D. conferticostata are only about half as wide as in the species from 

 San Giovanni Ilarione ; 2d, in the former there is not that alternation of 

 longer and shorter septa characteristic of the latter; 3d, in the Jamaican species 

 there is no series of fused knobs, corresponding to the inner termini of the 

 larger septa, on either side of the columella, and separated from it by a rather 

 deep furrow. After having made this comparison, it will be easily seen that 

 the two species are very distinct ; but the features that they have in common 

 show them to be closely related. 



Diploria conferticostata, var. columnaris, var. no v. 



Plate XXXIX. Fig. 4. 



In the preceding discussion, I have purposely omitted the consideration of 

 a specimen that seems to me to be a young one of B. conferticostata, with a 

 different mode of growth. The form is a short ascending column, about 

 38 mm. high, with the following dimensions. 28 mm. below the top : greater 

 diameter, 18 mm.; lesser, 12.5 mm. At the top the specimen is compressed 

 and has begun to bifurcate. Here the greater breadth is 22 mm. ; the lesser 

 varies from 2,5 to approximately 10 mm. The 10 mm. is the thickness of the 

 thicker branch. The series are very long and much wound. The distance 

 across the valleys is 1 to 1.5 mm. ; across the coUines about .5 mm. There are 

 about 30 costse or septa to 5 mm., — 60 to the centimeter. The depression on 

 the summit of the colline is usually very obscurely or not at all marked ; in 

 some places it is moderately distinct. These are the points of difference. 

 The specimen is evidently immature, and I am confident that it is only a 

 young, somewhat peculiar variety of the D. conferticostata. 



Locality. Catadupa, R. T. Hill, collector. 



Type of Variety. Museum of Comparative Zoology, Harvard University. 



VOL. XXXIV. 16 



