ON THE DEVELOPMENT OF TUBULIPOTlA. 89 



generic difference between Tubulipora and Idmonea can 

 be maintained, I shall regard the species described in this 

 paper as members of the genus Tubulipora. 



The type-species of Lamouroux' genus is Idmonea tri- 

 quetra, a fossil form from the '^ terrain a polypiers" (Ba- 

 thonian) of Caen. Tlie description might lead to the inference 

 that the species is erect, but Gregory (12, p. 134) states that it 

 is always an encrusting form, and has justly remarked that it 

 is therefore impossible to define Idmonea as consisting only 

 of erect species. If this is so, it becomes very difficult to draw 

 any line between Tubulipora and Idmonea. Dr. Gregory's 

 catalogue includes no species of Tubulipora, but he dis- 

 tinguishes (p. 134) a family Idmoniidse from the Tubuliporidse 

 mainly by the existence of regular transverse rows of zooecia 

 in the former. I do not think that this distinction can be 

 maintained, either as the character of a family or even of a 

 genus. Lamarck's type-species of Tubulipora was defined as 

 having its zooecia in transverse series, and this feature is 

 strongly marked in other recent species which are ordinarily 

 included in that genus. The only character in Dr. Gregory's 

 diagnosis of Idmonea (p. 134) which is not applicable to 

 many species of Tubulipora is the ridged or triangular cross- 

 section of the branches, and it is very doubtful if this is really 

 a valid generic difference. 



From a superficial examination of the ovicells of Idmonea 

 a tl an tic a, and from a consideration of Smitt's description 

 and figures (40, p. 443, pi. iv, figs. 5, 7), it appears to me that 

 this form at least is closely allied to T. liliacea. 



III. Synonymy, Diagnoses, and Accounts of the Species. 



The material on which the following account was based was 

 collected mainly in the Salcombe Estuary, in South Devon, in 

 March and April. I have to thank Dr. A. M. Norman for 

 having recommended me to choose that place as a base of 

 operations. Other specimens were collected by myself while 

 working at the Plymouth Laboratory and on other parts of 



