ON THE MADEEPOEARTAK GENUS ALVEOPOBA. 495 



Lampreys is absent in the Myxinoids, and that in the latter the 

 anus, "porus genitalis," and ureters open into an integumentary 

 cloacal chamber, similar to the cloacal chamber common to anus 

 and uro-geniial sinus in the Lamprey. 



EXPLANATION OF PLATE 32. 



Fig. 1. CloacBiX region oi Myxine glutinosa seen from the left side, X5. The 

 left wall of the cloaca and body-cavity has been i-emoTcd. sl.gl. 

 Slime-gland in upper lip of anus. 



Fig. 2. Cloacal region of Bdellostoma cirrhatum dissected in the same way as 

 fig. 1, X"A The left half of the pore only is seen. 



Beference Letters, 

 an. Anus. cl. Cloaca, cl.ex. Extension of cloaca, fb.bd. Fibrous band 

 surrounding abdominal pore. int. Intestine buried in body-wall. inf. 

 Intestine covered by peritoneum, l.sl.g. Lateral slime-glands, p.g. Porus 

 genitalis. t(,r. Ureter, ur.o. Urinary papilla, mes. Dorsal mesentery. 



On the Affinities of the Madreporarian Genus Alveopora with 

 the Palaeozoic Favositidce , together with a brief Sketch of 

 some of the Evolutionary Stages of the Madreporarian 

 Skeleton. By H. M. Beenaed, M.A. Cantab., F.L.S. 

 [Bead 16th December, 1897.] 

 (Plate 33.) 

 The genus Alveopora was founded by Quoy and Gaimard * for a 

 coral from New Ireland collected during the voyage of the 

 ' Astrolabe.' The original description given by these authors is 

 intelligible and accurate so far as it goes, but the figures appear 

 to have been drawn from memory, and certainly do not represent 

 any known species of Alveopora. 



The Madrepora retepora of Ellis and Solander, Eorskal's 

 Madrepora dcddalea, the coral so beautifully figured by Savigny 

 in his 'Description de I'Egypte ' (tab. iii. fig. 4), and certain of 

 Lamarck's types were soon recognized as specific forms of this 

 new genus. 



In 1848 Dana t boldly claimed the genus as belonging to the 

 Palaeozoic Eavositidse, which he classed as the second of his three 



* Voyage de FAstrolabe (Zoologie), iv. 1833, p. 240. 

 t 'Zoophytes,' p. 117. 



