4 o DISCOVERY REPORTS 



formity of the dactylozooids and the many intermediate forms bridging the differences between simple 



and spiniferous pores furnish evidence that dimorphism does not exist. 



The small gastropolvps (Figs. 6, 7) are tubular and have four to six rudimentary small tentacles 

 which are exceedingly difficult to trace in contracted specimens. 



Both male and female colonies are found in the Discovery material. The male colony (PI. II, fig. 2) 

 is much lighter coloured than the female (PI. Ill, fig. 1). This, however, may be fortuitous. On the 

 other hand, although the male ampullae are placed rather superficially on the branches, there is no 

 external indication of their presence, whereas the female ampullae are generally marked by lighter 

 coloured or whitish spots on the branch or, in many cases, also by feeble swellings. Nevertheless, the 

 ampullae do not show as protuberances among the pores or spines. 



The male ampulla contains two to four gonophores, one of which may be fully ripe, whereas the 

 second is less advanced in its development, the other gonophores being very small or quite rudimentary. 

 In half-ripe gonophores, where the spadix attains its greatest development, the spadix is saucer-shaped 

 with a small varying number of pouches or lobes, i.e. it is a simplified ' trophodisc '. The gonophores 

 bud from the basal part of a finger-shaped blastostyle similar to that observed in Distichopora violacea 

 (England, 1926) or Errina spongiosa (Broch, 1942), the agreement with the latter being especially 

 marked. 



While the male ampulla does not generally exceed 0-5 mm. in diameter, the r'vpe female ampulla has 

 a diameter of about 1 mm. or even a little more. As a rule only one ovum develops at a time in the 

 ampulla. No detailed study of the development of the gonophores was made, but they do not appear 

 to differ from the common types of gonophores among Stylasteridae (Broch, 1942). 



The present species cannot be assigned to any previously described form among the Stylasteridae. 

 The irregular distribution of gastropores and dactylopores proves that it belongs to the subfamily 

 Sporadoporinae, and the spines connected with several of the dactylopores, together with the arrange- 

 ment of these spines in terminal parts of the branches, suggest the genus Errina. However, a thorough 

 examination of the spines reveals that they differ from the regular spine types of Errina, from both 

 the nariform spines of Eu-Errina, and from the 'waterspouts' of Labiata (Broch, 1942). 



Above all, the colony is rather aberrant in its mode of growth. In some species of Errina various 

 authors have emphasized the occurrence of more or less incidental anastomoses between adjacent 

 branches of the colonies and used this as a specific characteristic. In the present species it is difficult 

 to detect a free branchlet even at the periphery of the net-like colony, and the growth form of the new 

 species seems to occupy a position among the Stylasteridae similar to that of the Retepora colonies 

 among the Bryozoans. It is accordingly reasonable to regard this mode of growth and branching as 

 a generic character, a point of view which to a certain degree is strengthened by the features of the 

 spines and their above-mentioned independence of special dactylopores and dactylozooids. It is 

 probable that the latter character should be more properly regarded as a specific feature. To settle 

 this question, however, comparison with other related species is needed. 



Hence the specimens can be regarded as the representative — and type — of a new genus, 



Errinopsis n.g., 



the characteristics of which at present coincide with the genotype : 



Errinopsis reticulum n.sp. 



Colony simple or composite flabelliform, the branches anastomosing to form a regular, fine mesh- 

 work. Gastropores and dactylopores irregularly scattered on all sides of the terminal branchlets; in 

 older parts of the branches the numbers of pores, and especially of dactylopores, diminish. Spines 



