60 - THE SPONGES. 



Parrea mexicana, sp. nov. 



Plate 7, Figs. 4, 6, 7, 8, 10. H. 



Dmgnosis. Habitus like that of Farrea occa. With oxyhexasters. Characteristic 

 dermal clavulae umbellate, with 12-16 teeth in the umbel. Gastral clavulae in part 

 umbellate like the dermal ; in part anchor-like with 4-5 teeth, the stalk usually with 2 

 lateral spines. Species close to F. aculeata F. E. Sch. 



Station 3430, 1 fragmentary specimen. 



The habitus, Fig. 7, Plate 7, is similar to that of Farrea occa. 

 The tube diameter is 8 mm. The dictyonal framework does not differ 

 from that of F. occa. In places it is one-layered, in other places two- 

 layered. Small oxyhexacts with rays 60-80 /i long are in places fused 

 with the framework. The fragment is obviously from the older part 

 of a stock. 



The dermal and gastral pentacts are alike (Fig. 8, Plate 7). The 

 proxhnal ray is slightly longer than the tangentials, which commonly 

 measure about 280 /x x 12 yu.. The rudimentary distal ray forms a small 

 rounded tubercle. In the majority of the spicules, the rays are smooth 

 except at the ends. In others the tangential rays bear very weak tubercles 

 over their whole surface. Occasionally spicules are found, in which the 

 tangential rays on their outer surface bear the well-known strong spinous 

 tubercles. 



The uncinates commonly exhibit the same difference between the two 

 ends which I have mentioned under Farrea occa claviformis. The spicules 

 vary greatly in size. Forms, 720 /i, x 5 ju, and larger ones up to twice this 

 size, occur. 



The oxyhexasters resemble those of F. occa, but are larger; and the 

 terminal rays, of which there are usually 2 or 3 to a principal, are as long 

 or nearly as long as the principal. The length of the latter is about 40 /x. 

 There is occasionally a surprising difference in length between the prin- 

 cipals of the same spicule. 



In Farrea aculeata F. E. Sch., Schulze (1899, p. 70) says the oxyhex- 

 asters do not essentially differ from those of F. occa. He mentions that 

 the number of terminals to a principal is 3, 2, or 1 ; and in the spicule 

 figured, the principal ray measures 35 /x in length, while the terminals 

 are about as long. Thus in the minute points of difference which the 



