106 



G. F. MATTEEAV: ILLUSTEATlOlSTS OF 



lobe. These spiues show most distinctly on the mould of the inner surface, and are 

 perhaps only perforations of the test. The outer surface of the test appears to the naked 

 eye to be smooth, biit when magnified it is found to be finely granulated. 



Varieties. 



This species varies much in the ornamentation of the cephalic shield. Beside the 

 type which is described by Prof. Hartt as having sparsely sown spines, there are three 

 varieties distingnished by the ornamentation. Of these, the first two appear to run into 

 the typical form, but the third has more stable characters. 



The spines which ornament the surface of Ct. Mattheivi are tubular, having a cavity 

 which passes through the test ; those on the front of the cheeks, on the frontal lobe, and 

 on the anterior marginal fold, are connected together within by a network of striations 

 which risually cross each other at the internal orifices of the spines ; on the outside of the 

 shield there are also striœ, though usiially ridges, corresjjonding in course and position to 

 those within. These striaî originate at the ocular lobe, and extend forward across the 

 anterior marginal fold to the edge of the shield. 



The following table, shewing the usual number of spines on different portions of the 

 test, will help to distinguish the varieties that are described separately after it ; — 



TABLE SHOWING THE AVERAGE NUjMBER OF SPINES OF DIFFERENT VARIETIES OF 



C'lENO CEPBAL US îfA TTHE WI. 



Typical form (young, 5x8 mm) 



" (well grown, 14 x 28 mm.) 



■< / 1 1* * i f 16 >^ 32 and \ 



Var. a. gcminispinosus (11 x 22 mm.).. . 



Var. /3. hispidus 



Var. >•. pirlmpidus 



Var. a. geminispinosus. A sparsely-spined variety in which the spines are paired on 

 many parts of the shield. This is especially the case with those on the occipital ring and 

 glabella, and in some cases there is a distinct double row of spines, passing from the outer 

 posterior angle of the cheek, inside the summit, to its anterior extremity, and thence 

 round the front of the frontal lobe to the opposite cheek. This variety may be the Cono- 

 cephalites geminispinosus of Prof. Hartt ; but the wide marginal fold and gibbous cheeks, 

 attributed by him to geminispinosus, are more frequently met with in the next variety. 



Var. /?. hispidus is more angulated in the outline of the cephalic shield than the typi- 

 cal form, and the middle of the anterior margin generally projects a little in front : it has 



