184 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 14 



Genus LYRULA Jullien, 1886 



Costules large, separated by broad furrows which extend across the 

 front ; orifice shaped like an inverted lyre. Avicularia interzooecial, large 

 and spatulate, often wanting. No ooecia. Dietellae wanting, but multi- 

 porous septules are present in both distal and lateral walls. Genotype, 

 Cribrilina hippocrepis Hincks. 



Lyrula hippocrepis (Hincks), 1882 

 Plate 27, figs. 7 and 8 



Cribrilina hippocrepis Hincks, 1882:470. 

 Cribrilina annulata, Robertson, 1900:326. 

 Cribrilina hippocrepis, Robertson, 1908:280. 

 Cribrilina hippocrepis, O'Donoghue, 1923:30. 

 Lepralia regularis, O'Donoghue, 1923:40. 

 Lyrula hippocrepis, O'Donoghue, 1926:52. 



The species has been well described by Hincks and by Robertson, but 

 without calling attention to the variability, which is very marked. In 

 older stages the calcification is exaggerated and takes various forms, one 

 of which led O'Donoghue to describe it as a new species, which he cor- 

 rected later (1926:52). 



Zoarium encrusting, or rarely erect and bilaminate. The zooecia are 

 regularly disposed in alternating series when not crowded ; distinct, but 

 the separating grooves may become filled in old specimens; moderately 

 large, 0.50 to 0.75 mm long by about 0.40 mm wide; ventricose when 

 young but becoming nearly flat with age. The pericyst is formed by 5 

 (4 to 6) pairs of broad costae, each with a large pore (pelma) at its 

 base; the separating grooves are broad and each bears 5 or 6 small slit- 

 like longitudinal lacunae. The distal costae, which form the aperture 

 bar, are unusually broad; there is no median umbo, but in older zooecia 

 there is often a lateral umbonate protuberance which develops in connec- 

 tion with the lateral costal pore. In older stages all of the lateral costal 

 pores may be surrounded by short, stout, erect collars. The aperture, 

 about 0.20 to 0.20 mm is widest and straight on its proximal border, 

 narrowed to form lateral indentations, then evenly rounded to conform 

 with the border of the operculum; the latter is well chitinized, with a 

 strong bordering sclerite, but incomplete proximally. 



Large vicarious avicularia, often wanting even in whole colonies, 

 occupy a position in the zooecial series ; the mandible long and subspatu- 

 late, with a long-triangular basal sclerite and attached without pivot or 

 cardelles. 



