39(S Albany Museum Records. 



Phacops acacia, iiov. sp. 



PI. X., Figs. 4, 4a. 



Phacops (Cryhaeus) africanus, Salter (pars.), Trans. Geol. 

 Soc, Ser. 2, Vol. VII., pi. XXV., fig. 5. 



Phacops crista-gaUi, Woodw., Lake, Ann. 8. A. Mus., 1904, 

 Vol. IV., p. 205, pi. XXIV., fig. f). 



This species bears the back ward I y directed genal spines 

 which Salter dotted in in two of his figures of the head of P. afri- 

 canus^. A third form is shown with the genal spines affixed, but 

 Lake 2 makes this into a new species, P. pujj/llus. There is no 

 statcnnent made as to the reasons which led Salter to dot in the 

 spines ; Lake, from a reexamination of Salter's tj'pes, states that 

 they are not there, at least in the original of fig. 6 ; the original of 

 fig. 1 cannot be identified. The neck segment bears a strong 

 median spine, as figured by Salter in fig. 6. 



The specimens in the Albany Museum consist of the impres- 

 sion of the lower part of the head and thorax in clay nodules, one 

 of which contains two heads. I abstracted a small portion of the 

 natural cast of the head of one of these which I figure. I attempted 

 to take a cast of the impression of the more complete head, but 

 there are so many projections overhanging the cavities that I was 

 unable to make a satisfactory replica of the original. I then tried 

 to take casts of portions separately, but the hollows where the 

 genal spines were once, formed air-cushions, which prevented the 

 material from entering, and I repeatedly obtained casts showing 

 the genal angles rounded. It was only by first filling in the hol- 

 lows of the spines that I was enabled to ultimately obtain a true 

 representation of the original. This fact may perhaps explain 

 why the natural internal casts of the head do not show the spines, 

 but possibly Salter, with an impression of the exterior to judge 

 from, dotted in the spines. If this theory of mine is correct, P. 

 africatiAis will have to be re-defined, and my species P. acacia 

 will have to drop out. In other words, P. africamis, Salter, 



'Salter, J.W., Trans. Geol. Soc, 185G, 2nd Ser., Vol. VII., pi. XXV., 

 figs. 1 and 6. 



^Lake, P., Ann. S.A. Mus., Vol. IV., 1904, p. 203, pi. XXIV , fig. 1. 



