POLYZOA FROM THE LIAS. 



633 



Amongst some specimens from the latter locality in my own cabinet 

 are numerous examples which both Mr. Yine and myself consider 

 to be distinct from Tate's type ; and to the consideration of them and 

 associated forms these notes are directed. 



Inasmuch as, with the Cyclostomatous Polyzoa, the simple cell- 

 structure makes it necessary for the student to adopt in great degree 

 zoarial growth as a means of classification, there occasionally occur 

 forms, as in the species under notice, which find no secure resting- 

 place under any family roof. In other examples, from the Inferior 

 Oolite, this difficulty is equally apparent. 



Ttjbtjlipoea inconstans, sp. nov. (PI. XXV. figs. 1-9 & 12.) 



Rarely does a form present more varying and erratic modes of 

 growth than the species before us. Whilst some colonies have a 

 foliaceous habit (fig. 1), others are cylindrical (fig. 5), after the 

 fashion of Diastojpora Lamourouxi, M.-Edw., though the predomi- 

 nant form of growth is erect, ramose, and cylindrical (figs. 4 and 7). 

 In some instances from the flattened lobes spring branches cylindri- 

 cal or but slightly flattened (fig. 8), and occasionally the colony is 

 adnate. 



The zocecia are long, with proximal extremities free for as much 

 as ^ or \ of their whole length (fig. 7), or else have but a slight 

 degree of projection from the stem. The peristomes are circular 

 (fig. 2), opening irregularly over the zoarium, and are about two 

 thirds of the diameter of the zocecia. Bright and distinct purple 

 lines separate the cells in marked contrast to the fawn-colour of the 

 cells themselves. Covering the whole surface are tubular papillae 

 or minute projecting tubes (surface-pores), arranged occasionally 

 in transverse or subspiral lines. The pores seem communicate 

 with the interior of the cell and are apparently connected with 

 each other by delicate tubes (fig. 3), which traverse the outer wall 

 mainly in the direction of the length of the cell. These surface- 

 pores, common to many families of the Polyzoa, are almost iden- 

 tical with the markings upon some Italian Proboscince. 



The zocecia of both foliaceous and cylindrical forms bear just 

 within the peristome solid circular closures (fig. 2). Though there 

 appear to be no absolutely terminal closed cells, yet, immediately 

 below the extremity of the newest branch, cells are often provided 

 with the closures — a point rather against the theory of their 

 development being only on old and worn-out cells. The position of 

 this calcareous cover below the orifice tells also somewhat against 

 its being considered a movable operculum. In its centre is a 

 funnel-shaped perforation measuring about one third of the width 

 of the whole, and there are also a few scattered minor perforations. 

 Frequently a slight constriction of the zooecial tube may be noted 

 below the position of the closure. 



Prof. Busk * figures species of Pustulopora and Patinella with the 

 zooecial tubes closed with calcareous lids, which are placed quite 



* 'The Polyzoa of the Crag,' by Gr. Busk, pi. xviii. fig. 2, pi. xix. fig. 1, Mem. 

 Pal. Soc. 



Q.J.G.S. No. 172. 2x 



