TKANSACTIONS OF SECTION C. 697 



F.R.S., at St. David's and elsewhere, have added an extenjive series of organisms 

 to these lower roclcs. The Longmynd group, which elsewhere had only yielded 

 annelide burrows and a portion of a trilobite, had at St. David's furnished a sponge, 

 two ostracods, six trilobites, two litiffidellce, and two thecae. 



The Menevian beds at St. David's have made known three sponges, one echino- 

 derm, twenty-five trilobites, five pteropods, and three brachiopods. No fewer than 

 twenty-five genera and eighty-five species of trUobites are now recorded from the 

 Longmynds up to the Tremaiioc slates. Dr. Hicks observes that the Longmynds 

 have yielded a few indications of life in Shropshire and North Wales, but these 

 beds require to be further explored. 



Thejirst trilobite in the green slates of Bangor was discovered by two work- 

 men and recorded by Professor J. J. Dobbie, of the University College of North 

 Wales, Bangor, on 5th August last. Two specimens have been obtained, the second 

 by Profesf-or Dobbie himself. 



The most perfect is 3i inches long and If broad, and shows both the intaglio 

 and relievo. 



The margin of the head shield is rounded ; the glabella has three lateral furrows ; 

 there are fourteen free thoracic rings and a short pygidium, consisting of about three 

 coalesced segments. 



After a careful comparison with Conocoryphc, Olenus, Paradoxides, Angelina, 

 &c., the author concludes to place the Bangor trilobite in the genus Conocoryphe, 

 and names it Conocoryphe viola. 



Horizon : Upper Green Slates. 



' Llanberis Grits and Slates,' Harlech and Longmynd Rocks. 



Loc. : Penrhyn Slate Quarry, Bangor, North Wales. 



4. Fifth Reiyort on the Fossil Fhylhpoda of the Palceozoic Bocks. — See 

 Reports, p. GO. 



5. On the Mode of Fevelopment of the Young in Plesiosaurus. 

 By Professor H. G. Seelet, F.U.S. 



^ This paper was descriptive of a specimen submitted to the author by J. F. 

 Walker, Esq., F.G.S. It is a phosphatised nodule from the Lias of Whitby, 

 measuring about 10 centimetres by 7 by 5. On its surface are four more or less 

 complete specimens regarded as foetal plesiosaurs, together with fragments of at 

 least three others. They are remarkable for having the flesh mineralised with 

 phosphate of lime, and still show many characters of the external form of the 

 body, but slightly distorted by decomposition. Only one individual has the head 

 preserved : its extreme length is about 14 mm. The nares are terminal like those 

 of an emydian chelonian. The eyes look obliquely upward and outward. The 

 superior aspect of the head behind the frontal bone is occupied by muscular 

 substance. The skull rests on one side against the matrix, so that its transverse 

 width is not clearly shown ; but it was wider than the neck, and narrows in front 

 of the orbit towards the nares, which curve a little downward. The eyes look 

 obliquely upward and outward, and have a diameter of two millimetres. The 

 neck has a length of 4-5 centimetres. Behind the head it is about four millimetres 

 deep and as wide ; it widens to a centimetre where the expansion takes place at 

 the shoulders, and there the depth is about eight millimetres. A sharp median 

 ridge down the middle of the neck divides its superior aspect into two oblique mode- 

 rately convex surfaces. Other individuals sbow that this ridge was prolonged 

 down the back and tail, but less elevated. The body is about as long as the 

 neck. On the right side it has suffered some abrasion and injury in cleaning, and 

 is not quite symmetrical, being a little larger on the left side. It is about 2-4 

 centimetres wide, convex from side to side, and less convex in length. The ex- 

 pansion from the neck is rapid, and attenuation posteriorly is marked, so that the 

 body has a long egg-shape. The tail appears to be short and conical, and curves 



