108 REC?ORDS OF THE ATJSTRALIAN MUSEUM. 



The varieties secunda and tertia, of Thorecta exemplum, Lenden- 

 feld, are very soft and elastic, whilst the var. prima (tenuis), 

 Hyatt, is hard, rigid, and possesses very little elasticity. 



Thorecta erecta, Hyatt. 



(Plate xiv., figs. 29, 29a - e). 



Spongelia rectilinea, var. erecta, Hyatt, Mem. Bost. Soc. Nat. 

 Hist., ii., (4), 1877, p. 537, pi. xvii., tigs. 12-13. 



Thorecta exemplum, var. secunda, Lendenfeld, Aust. Mus. Cat., 

 xiii., Sponges, 1888, p. 145; id., Mon. Horny Sponges, 1889, 

 p. 359, pi. xxiv., figs. 3 — 5. 



Thorecta exemplum,, var. tertia, Lendenfeld, Aust. Mus. Cat., xiii , 

 Sponges, 1888, p. 145; id., Mon. Horny Sponges, 1889, p. 

 359, pi. xxiv., figs. 3 - 5, pi. xxxiii., figs. 2, 3, 4, 6, 7, 10. 



This species is represented by numerous examples, which exhibit 

 great variation in habit. There are also six specimens, named by 

 Dr. Lendenfeld, labelled Tliorecta exemplum, var. tertia, Lenden- 

 feld, and two bearing the name of Thorecta exemplum, var. secunda, 

 Lendenfeld. The former are numbered as follows: — Nos. 65, 75, 

 7G, 78, 79, 80, and in each case they agree with the diagnosis. 

 Hyatt's description introduces an element of doubt as to whether 

 his examples are identical with the variety tertia, Lendenfeld. 

 According to the latter author, "The body of the sponge itself 

 appears massive, conical, irregular, distended above. It attains 



a largest horizontal transverse diameter of 50 mm." "Each 



osculum is slightly prominent. In large specimens there is gener- 

 ally one large osculum in the middle which measures 10 — 15 mm. 

 in diameter, and a number of small oscular scattered around it." 

 It will be noted that there is no mention made of a cup-like 

 cavity at the summit, yet Hyatt's account states that "The inside 

 of the cup is very shallow." From the above quotations and the 

 specimens under examination, it appears to my mind that both 

 forms are simply extreme variations of one species. There is a 

 regular graduated series connecting the conical forms with those 

 that are cup-shaped. Certain characters are common to both 

 forms; these are: deep pits on the outer surface, a large central 

 osculum (which may be seated on a conical elevation or at the 

 bottom of a cup-like depression), and either with a series of smaller 

 ones arranged around it, as in the latter, or with one or two 

 occupying the lateral aspect of the ridge in those that are conical. 

 The texture of the sponge is the same, and the contents of the 

 fibres consist of large sand grains and foreign spicules. 



The following brief descriptions will convey some idea of the 

 variation exhibited by this species, all of which are more or less 

 distinctly pedunculate : — 



