BACTEONELLA. 205 



Incertce sedis. 



Genus BACTEONELLA, Einde, n. g. 



Sponges simple, rod- or club-shaped, usually attached by a slightly expanded base. 

 The lower portion exhibits traces of a wrinkled compact dermal layer ; the rest of the 

 surface is smooth and covered with minute circular and subangular apertures, which 

 appear to be bounded by a delicate open dermal layer of three- or four-rayed spicules. 

 The sponge appears to be throughout composed of spicules, not arranged in fibres, 

 but forming an open tissue with irregular interspaces. The exterior portion is 

 penetrated by definite cylindrical canals which can be traced for a short distance 

 into the interior, though they do not appear to extend into the central portion of 

 the sponge. The spicules are so closely intermingled in the exterior portion that 

 only circular sections of the rays, and rarely a portion of a conical ray, can be distin- 

 guished ; but in the central portion the spicules are less intricately associated, and 

 definite three- and probably four- rayed forms can be distinguished. The rays of 

 some of these spicules are clearly microspined. Mingled with the definite spicules 

 are smaller forms which appear to be of an irregular character, though the condition 

 of the specimen prevents accurate determination. In transverse sections the interior 

 portion of the sponge is partially filled with a dark earthy matrix, and appears to 

 possess a diff"erent structure to the exterior, but this is probably owing to the more 

 compact agglomeration of the spicules near the surface. 



This genus is based on the characters of the small Jurassic sponges which form 

 part of Goldfuss's species Ceriopora clavata, Petref. 1 Th. p. 36, 1. 10. f. 15c-_/'(non 

 f. ff, b). The minute structure of these forms can only partially be made out in 

 thin microscopic sections, but sufficient is shown to indicate that it materially differs 

 from that of the fossil Calcareous sponges already described. The absence of a fibrous 

 arrangement of the spicules distinguishes it from the Pharetrones ; whilst the structure 

 of the wall and the absence of a central cloaca separates it from the Sycones. The 

 disposition of the spicules more nearly resembles that of the recent Leucones ; but in 

 none of the existing examples of this family are the three-rayed spicules microspined. 

 As the genus cannot suitably be included in any of the present divisions of the Calca- 

 reous sponges, I propose to leave it in an indefinite position until its characters are 

 more clearly ascertained. 



Bactronella pusillum, Hinde, n. sp. (Plate XXXVIII. figs. 3, 3 a-g.) 



1826-33. Ceriopora clavata, Goldf. pars, Petref. 1 Tli. p. 30, t. 10. f. 15 c-f (non f. a, b). 

 1858. Ceriopora clavata, Quenst. Der Jura, p. 665, t. 81. f. 59, 60. 

 1881. Ceriopora clavata, Quenst. Petref. Bd. 6, p. 245, t. 152. f. 63-88. 



Subcylindrical or slightly inflated sponges, with conical summits, varying from 3 "5 



