628 SUMMARY OF CURRENT RESEARCHES RELATING TO 



finds on Clare Island was Gallidina asperula, a species only recently 

 discovered in Canada. The most important peculiarity of the Irish 

 Bdelloid fauna is to be found in certain varieties of common species. 

 These occur among the spiny Bdelloids, which are found in the genera 

 Dissotrocha, Pleuretra, and Gallidina. 



Echinoderma. 



Structure of Solaster endeca.*— James F. Gemmill contributes 

 some notes on the structure of this starfish. 1. The central set of pore 

 canals of the madreporite open into collecting trunks leading into the 

 ampullary part of the axial sinus which leads directly into the stone 

 canal. 2. The marginal set of pore canals form collecting trunks which 

 lead into the upper end of the axial sinus, and also communicate freely 

 with the ampullary chamber. 3. In the strict sense none of the pore 

 canals of the madreporite can be said to open into the stone canal. 

 There is an interesting blind diverticulum from one of the spaces con- 

 nected with the central chamber, which invaginates the wall of the dorsal 

 sac and expands within its cavity. It may serve as a channel for the 

 escape of wandering cells from the dorsal sac. The anus in Solaster 

 occupies the same relative position as in other starfish, i.e. it comes after 

 ray V. In four gonads of a large specimen carefully studied, three had 

 two external openings, while the remaining one had three. The external 

 openings formed slit-like pits, and each received the ends of two or three 

 main ducts. Traced inwards, these ducts, after passing through the body- 

 wall, divided into branches each of which came into relation with one of 

 the small ultimate clusters of egg-tubes. The author also discusses the 

 aboral perihamial sinus and an interbrachial branch of the external oral 

 circular sinus. 



Middle Cambrian Holothurians.f — C. D. Walcott has discovered 

 some entire Holothurians in fine-grained silico-argillaceous rock from 

 British Columbia. Their occurrence records for the first time, apart 

 from some scattered calcareous spicules and plates, the presence of this 

 class of organisms in any geological formation. He establishes a new 

 family, Eldoniidse, for a free-swimming form, Eldonia ludwigi g. et sp. n. 

 The body was disc-like, the mouth and anus ventral, the water-vascular 

 system radial from the aboral pole. There was a broad band of con- 

 centric muscle-fibres on the outer half of the subumbrella surface. There 

 was no calcareous skeleton. It was found associated with Trilobites, 

 Phyllopods, and Sponges, and was first regarded as a Medusa. 



Another form is Laggania cambria g. etsp. n., with an elongate, pear- 

 shaped body. The ventral mouth, situated near the anterior end, was 

 probably surrounded by calcareous plates. In Louisella pedunculate 

 L r . et sp. n. the ventral sole is beautifully outlined by the marginal row 

 of podia on each side. A new Synaptid, Mackenzia costalis g. et sp. n., 

 has an elongated cylindrical body, and the plates around the anterior 

 end are preserved as casts on the rock. In none of the forms was there 

 any trace of calcareous matter. 



* Proc. R.Phys. Soc. Edinburgh, xviii. (1911) pp. 174-91 (8 figs.). 



+ Smithsonian Misc. Coll., Ivii. (1911) No. 3, pp. 41-66 (6 pis. and 6 figs.). 



